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RAY100 answered: 1636 problems
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Expressions-with-variables/192356: if y=8x^2 + 4x-1 is expressed in the form y=a(x-h)^2+k, where a, h, and k are constants, what is the value of k ?
1 solutions

Answer 144402 by RAY100(1637) About Me  on 2009-04-21 13:47:54 (Show Source):
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y=8x^2+4x-1 to form y=a(x-h)^2+k
y=8(x^2+x/2)-1
now must complete square of bracket terms
y=8(x^2 +x/2 +1/16) -1 -8(1/16)
simplify
y=8(x+1/4)^2-1.5
this fits form with
a=(8)
h=(-1/4)
k=(-1.5)
checking
let x=3 solve for y
initial eqn y=8x^2+4x-1= 8(3^2) +4(3)-1=72+12-1=83
final form y=8(x+1/4)^2-1.5=8(3.25)^2-1.5= 8(10.5625)-1.5=84.5-1.5=83 ok
to complete the square we take coefficient of middle term, divide by two, and square it
ie (1/2) , (1/2)/2=1/4, (1/4)^2=(1/16)
this becomes constant term of "square"
since we added this to complete square terms we must subst from constant term to balance eqn. In this case we added 8(1/16) in total therefore we substract (8/16) from constant


logarithm/192355: log5 square root of 125 - log2 square root of 2=
1 solutions

Answer 144393 by RAY100(1637) About Me  on 2009-04-21 13:10:21 (Show Source):
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basic form is log base a of b = ( log b)/(loga)
log base 5 of sq rt 125 - log base 2 of sq rt 2
log of neg number is undefined therefore only use positive sq rts
(log sq rt 125 / log 5 ) -(log sq rt 2/ log 2)
(log 11.18/log5) - (log 1.414/log2)
1.5-.5
1.0


Rational-functions/192330: 3+(sqroot5x-1)=x
1 solutions

Answer 144389 by RAY100(1637) About Me  on 2009-04-21 12:56:54 (Show Source):
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3+sq rt (5x-1) = x
subt 3 each side
sq rt(5x-1) = x-3
sq both sides
+-(5x-1) = (X-3)^2
USING ONLY + answer ( - answer gives imaginary answers)
+(5x-1) = (x-3)(x-3)= x^2-6x+9
subt 5x each side
-1 = x^2 -6x +9 -5x
add 1 to each side
0= X^2 -6x +9 -5x +1
simplifying
0=x^2 -11x +10
factoring
0=(x-10)(x-1)
x=10 and x=1
checking
3 +sq rt (5x-1) = x
3 + sq rt (5(1)-1) = (1)
3 + sqrt 4=1
3+-2 =1 ok with -2
for x=10
3+sqrt (5(10)-1) = (10)
3+ sqrt 49 =10
3+-7=10 ok with +7


Travel_Word_Problems/192352: A pole that is 2.9 tall casts a shadow that is 1.58 long. At the same time a nearby tower casts a shadow that is 50.5 long. How tall is the tower? Round your answer to the nearest meter.
1 solutions

Answer 144386 by RAY100(1637) About Me  on 2009-04-21 12:35:47 (Show Source):
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if a drawing were made showing a line from a point on the ground thru top of tower and then thru top of bldg, we could see two similar triangles. Similar triangles have sides proportional.
in our case h/50.5=2.9/1.58
cross multiplying
1.58 *h=50.5 * 2.9
1.58 *h = 146.45
divide by 1.58
h=92.68987= 92.69


Numeric_Fractions/192349: What is the angle between the arrows of a clock at 3:15? Record your answer
as precisely as possible. (Hint: The arrows are not at exactly the same place.)

1 solutions

Answer 144384 by RAY100(1637) About Me  on 2009-04-21 12:27:38 (Show Source):
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assume the 3:15 is 3 hrs and 15 minutes from zero. AM or PM is not given.
The hr hand has rotated once for every hour plus 90 degrees for 15 minutes or
hr = 360 *3 +90 = 1170 degrees.
the minute hand has rotated 60 times for each hour plus 90 degrees for 15 minutes or
minute hand = 3 *60*360 +90= 64,890 degrees
The difference is 63,720


Numeric_Fractions/192350: Robinson’s dining room has a square base. The perimeter is 144 feet, how
long is each side?

1 solutions

Answer 144381 by RAY100(1637) About Me  on 2009-04-21 12:15:17 (Show Source):
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the definition of a square defines each side as equal
per = 2l +2w for rectangle, but square is l=w, or per =4s
per=4s
144 = 4s
divide by 4
36=s (ft)


Circles/192331: x^2+4x+y^2+6y=2
What is the center and the radius?
1 solutions

Answer 144379 by RAY100(1637) About Me  on 2009-04-21 12:10:49 (Show Source):
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basic formula for a circle is
(x-h)^2 + (y-k)^2 = r^2, where h is x center, k is y center, r is radius
to fit this form the given problem must "complete the square"
(x^2 +4x +4) + (y^2 +6y+9) = 2 + (+4)+ (+9)
reviewing take coefficient of the middle term, 4x, divide by 2 and then square, (4/2)^2 =4 and add to both sides of eqn
for y terms, ( 6/2)^2 =9 and add to both sides
Now factor x and y sets
(x+2)^2 + (y+3)^2 = 15
comparing to basic form we find
x center is (-2)
y center is (-3)
rad^2 = 15, rad =sq rt 15 = 3.87


Numeric_Fractions/192346: Jenny’s trunk has a length of 100 inches, and a width of 20 inches. She
knows from the manufacturer that the volume of her trunk is 20000 cubic
inches. What is the height of the trunk?

1 solutions

Answer 144376 by RAY100(1637) About Me  on 2009-04-21 11:52:27 (Show Source):
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volume = length * width * height
or V=l*W*H
for given info
20,000= (100) (20) *H
20,000=2,000*H
10=H


Polynomials-and-rational-expressions/192341: This question is from textbook Intermediate Algebra
Find the opposite of the polynomial : –2r^2 – r + 3
Do we just reverse from posistive to negative or is there a method?
1 solutions

Answer 144374 by RAY100(1637) About Me  on 2009-04-21 11:47:42 (Show Source):
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Opposites are just as you stated. Just opposite sign. The two add to zero.
Normally with polynomials, we talk about inverses. This is the reflextion over y=x. We usually find these by setting x=y, and y=x.
For example if y=2x, inverse is x=2y or y=x/2.


Quadratic_Equations/192340: I'm having problems with this type of question
Find the height, of a ball, above ground using the following information.
wait 3 seconds, velocity is 45 ft/sec, initial height above ground is 10 ft
wait 2 seconds, velocity is 95 ft/sec, initial height above ground is 50 ft
1 solutions

Answer 144368 by RAY100(1637) About Me  on 2009-04-21 11:19:21 (Show Source):
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This is a physics problem under "projectile motion"
Sometimes it is found in algebra under quadratic topics as a actual application example.
For today, we are asked how high the projectile will go, in a given time, with an initial velocity. The velocity provides the upward energy, and gravity provides the downward energy.

Usually, the angle of the initial velocity is important, but for today we will assume straight up.
If not, let me know.
The basic eqn is:
delta y = v*t - (1/2) (32.2) t^2
where :
delta y is change in height. Note as time progresses, the projectile goes up, reaches a peak, and then comes down.
v is initial velocity. units in this case are ft per sec or ft/sec
t is elapsed time. units are sec
32.2 is gravity. we are using English today. be careful of metric. english units are 32.2 ft per sec squared, or 32.2 ft/sec^2 (metric is 9.8 m/sec^2)
1/2 is a constant to get average acceleration

1st problem
y= vt-1/2 (32.2) t^2
= (45) (3) - 1/2 (32.2) (3^2)
= 135 - 144.9
= (-9.9) ft
Note we started at 10 ft above ground, therefore 10-9.9 = (.1) ft above ground
This is not so nice a first problem. The projectile has been in the air long enough to go fully up, stop, and now decend to just above ground height.
Additional calc shows that the projectile goes up to a peak of about 31.4 ft in 1.4 sec before starting down.
2nd problem
y=vt-16.1t^2 = 95*2 -16.1 * 2^2= 190-64.4=125.6 ft
Again, initial height was 50 ft, therefore final position is 50+125.6 =175.6 ft
additional calc shows peak at about 3 sec of about 140 ft


Expressions-with-variables/192200: This question is from textbook Algebra 1
Please help, I'm very frustrated and don't understand how to solve linear systems with substitution. I have a lot of homework due tomorrow and don't understand what I'm supposed to do.
x-y=0
12x-5y=-21
1 solutions

Answer 144246 by RAY100(1637) About Me  on 2009-04-20 16:47:52 (Show Source):
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1) x-y=0
2) 12x-5y=-21
In substitution we use one eqn to establish a x to y relationship.
Then we substitute this relationship in the other eqn
for example from (1) we know x-y=0, therefore x=y
substituting into (2)
12 (y) -5y = -21
simplify
7y=-21
divide by 7
y=(-3)
substitute this in either (1) or (2) to find x
using (1) x-y=0
x-(-3) =0
y=(-3)
checking
(1) (-3)-(-3)=0 ok
(2) 12(-3) -5(-3) =-21
-36 +15 = -21 ok


logarithm/192198: Find the solution of the equation, correct to two decimal places: 5Ln(1-x)= 8
1 solutions

Answer 144242 by RAY100(1637) About Me  on 2009-04-20 16:37:54 (Show Source):
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5ln(1-x) =8
ln(1-x)^5 =8
e^8=(1-x)^5
2980.958=(1-x)^5
taking 5th root
4.95303 = (1-x)
subt 1 both sides
3.95303 =-x
x=(-3.95303)
checking
5 ln (1-(-3.95303) )=8
5ln 4.95303 =8
5(1.5999) =8
8=8 ok
to 2 dec places x= (-3.95)


Rational-functions/192035: In the equation 5x/(x+1), what is the end behavior? We are being taught the Ratey method and when I get to the E part of Ratey, i simplify it to 5/1. Does that make it top heavy? If so how do you determine the vertical asymptote?
1 solutions

Answer 144219 by RAY100(1637) About Me  on 2009-04-20 15:45:45 (Show Source):
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5x /(x+1)
vertical asymptote at den =0, x+1=0, x=-1
as degrees num and den equal, hor asymptote at 5/1 = +5
sketch vertical line at x=-1, and horizontal line at y=+5
rough sketch shows function starting low at x=-1, rising to rt thru (0,0) to just under asy y=5
starting high at x=-1, function decays to just above hor asy at y=5 as it goes to left
end behavior: as x approaches -infinity, y approaches +5 from +side
as x approaches + infinity, y approaches +5 from - side


Geometry_Word_Problems/192077: Given (triangle)ABC~(tringle)XYZ, AB=9, BC=18 and AC-21. If the perimeter of (triangle)XYZ is 112, find the measures of the three sides of (triangle)XYZ.
1 solutions

Answer 144216 by RAY100(1637) About Me  on 2009-04-20 15:29:57 (Show Source):
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Draw a rough sketch of two similar triangles
label sides carefully
as triangles are similar, sides are proportional
per of given triangle abc = 9 + 18 + 21 = 48.
per of new triangle is 112
as perimeters vary as scale factor to 1st power
sf = 112/48 =2 1/3 =7/3
xy = (7/3)ab =7/3 * 9 = 21
yz = (7/3) bc = 7/3*18 = 42
xz = (7/3) ac = 7/3*21 = 49
checking per 2nd triangle = 21+42+49= 112 ok


Equations/192180: I am having issues figuring out the inverse variation. Here is the problem
Suppose z varies inversely with t and that z=12 and t=10. What is the value of z when t = 6
1 solutions

Answer 144213 by RAY100(1637) About Me  on 2009-04-20 15:19:02 (Show Source):
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z= k/t
12 =k/10
cross multiply
k=120
now proportion is
z=120/t
for t=6
z=120/6 = 20


Linear-systems/192176: Could you help me with the following problem?
Solve the system algebraically.
5x+2y=10
3x+2y=6
Make sure there are no spaces in your answer. Be sure to include a comma.
Answer{( )}
1 solutions

Answer 144209 by RAY100(1637) About Me  on 2009-04-20 15:15:11 (Show Source):
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1) 5x +2y = 10
2) 3x +2y =6
subt (1) - (2)
2x =4
divide by 2
x=2
subst in (1)
5(2) +2y =10
10 +2y =10
subt 10 both sides
2y =0
y=0
answer (2,0)
checking
1) 5(2) +2(0) =10 ok
2) 3(2) = 2(0) =6 ok


Linear-systems/192172: Please help me solve....
(y-1)-y=y+1
1 solutions

Answer 144206 by RAY100(1637) About Me  on 2009-04-20 15:08:03 (Show Source):
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(y-1) -y =y+1
simplify by combining like terms
-1 =y+1
subt 1 from both sides
-2=y
checking
(y-1)-y=y+1
( (-2) -1) -(-2) = (-2) +1
-3 +2 = -2 +1
-1 =-1 ok


Polynomials-and-rational-expressions/192169: Can you please help me solve this problem?
5/2x+1/4x=7/4+x
Thank you so much; I really appreciate your help!
1 solutions

Answer 144203 by RAY100(1637) About Me  on 2009-04-20 14:58:43 (Show Source):
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(5/2)x +(1/4)x =(7/4) +x
Multiply by 4
10x +x=7+4x
7x=7
x=1
check
5/2 +1/4 =7/4 +1
10/4 +1/4 =7/4 +4/4
11/4 = 11/4 ok
if you really did mean
5/(2x) +1/(4x) =7/4 +x
mult by 4x
10 +1 = 7x +4x^2
0= 4x^2 -7x -11
0= (4x+11) (x-1)
x=(1) and x=(-11/4)
checking x=1
5/2 +1/4 =7/4 +1 ok
checking x=( -11/4)
5/-22/4 +1/-44/4 = 7/4 -11/4
-20/22 -2/22 = -4/4
-22/22 =-4/4 ok


Polynomials-and-rational-expressions/192167: Can you please help me solve this problem?
6-2x=5x-9x+2
Thank you so much; I really appreciate your help!
1 solutions

Answer 144202 by RAY100(1637) About Me  on 2009-04-20 14:42:37 (Show Source):
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6-2x=5x-9x+2
6-2x = -4x +2
add(2x) and subt (2)
4=-2x
divide by (-2)
x=(-2)
check
6-2(-2)=5(-2) -9(-2) +2
6+4=-10 +18 +2
10=10 ok


Polynomials-and-rational-expressions/192163: Factor.
-14w+2w^2+wz-7z
1 solutions

Answer 144199 by RAY100(1637) About Me  on 2009-04-20 14:37:19 (Show Source):
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-14w +2w^2 +wz-7z
reorder
2w^2 -14w + wz-7z
factor by grouping
2w(w-7) + z(w-7)
(2w+z) (w-7)
check by FOIL
2w^2 -14w +zw -7z


Equations/192165: can you square a negative number?
im trying to solve the equation
x^2+25=0
1 solutions

Answer 144198 by RAY100(1637) About Me  on 2009-04-20 14:29:46 (Show Source):
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an imaginary number (i) is = sq rt (-1)
x^2 +25 =0
x^2 = -25
x = +- 5 sq rt (-1) = +- 5i


Equations/192161: I home school and I am stuck on a problem.
all the information the directions give me is "solve each equation"
The worksheet is on radical equations' graphs, and complex numbers
Please help me solve this equation:
(2x-3)^2=-24
1 solutions

Answer 144197 by RAY100(1637) About Me  on 2009-04-20 14:25:56 (Show Source):
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(2x-3)^2=24
take sq rt of both sides
2x-3 = sq rt 24 = +- (4.899)
2x-3 =+4.899
2x = 7.899
x= 3.95
or 2x-3= -4.899
2x = -1.899
x=-.95
checking
(2(3.95) -3 )^2= 24 ok
( 2(-.95) -3)^2 =24 ok


Proportions/192130: This question is from textbook
For the following problem you need to give a proportion whose solution gives the answer to the problem. You must name the variable that you used in the proportion.
A lawyer bills her clients $300 per hour of service. If a client's case requires 17 hours to complete, use a proportion to calculate how much the client will owe the lawyer (excluding tax)
Thank You to all!
1 solutions

Answer 144195 by RAY100(1637) About Me  on 2009-04-20 14:09:44 (Show Source):
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Let x = cost of 17 hrs labor
300/1=x/17
cross mult
300*17=$ 5100 =x


Functions/192158: Find the domain of f(x) = 5x+1/x^2+5x-14
1 solutions

Answer 144193 by RAY100(1637) About Me  on 2009-04-20 14:02:54 (Show Source):
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(5x+1)/ (x^2+5x-14)
(5x+1) / ( (x+7) (x-2) )
therefore Domain is all Real numbers except, x=(-7) and x=(2)


Rational-functions/192141: For each rational function, identify any holes or horizontal or vertical asymptotes of its graph.
y= -2(x-8)/(8-x)
I have tried a couple different things, but I am not sure if any of them are correct.
First attempt:
There would be a vertical asymptote at x=8.
There would be a horizontal asymptote at y=-2.
Second attempt:
There would be a hole at (8,2)
Third attempt:
There would vertical asymptote at x=8.
There would be a horizontal asymptote at y=2.
I am extremely confused any help would be greatly appreciated!
1 solutions

Answer 144190 by RAY100(1637) About Me  on 2009-04-20 13:53:28 (Show Source):
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good work
an easier approach might be
y=-2(x-8)/(8-x)
simplify to
y= 2(x-8) / (x-8)
cancelling (x-8) 's gives us y=+2 but with a hole at x=8
no vertical asymptotes ( ie den =0)
no real horizontal asymptotes except y does always =2
review of horiz asymptotes, y = a(n)x^n +..... / b(m) x^m +.....
if n less than m, hor asy at y=0
if n=m, hor asy at y=a(n)/b(m)
and if n>m, no hor asy


Problems-with-consecutive-odd-even-integers/192149: find two consecutive odd integers such that the square of the larger is 3 than 12 times the smaller

x, x+2
1 solutions

Answer 144186 by RAY100(1637) About Me  on 2009-04-20 13:35:14 (Show Source):
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let smaller +x
let larger = x+2
The problem only makes sense if " is three than" reads " is 3 smaller than"
to solve this problem
l^2 = 12 S-3
(x+2)^2 =12(x) -3
x^2 +4x+4 =12x -3
subt 12 x both sides
x^2 +4x -12x +4 =-3
now add 3 to both sides
x^2 +4x -12x +4 +3 =0
x^2 -8x +7 =0
factoring
(x-7) (x-1) =0
setting both =0
x-7=0, x=7 (smaller) & larger =9
or x-1=0, x=1 (smaller) & larger is 3
checking (l^2=12*s-3)
3^2=12(1)-3 ok
9^2 = 12(7)-3 or 81=84-3 ok
Therefore both sets are correct, 1 &3, and 7&9


Polynomials-and-rational-expressions/192140: This question is from textbook saxon algebra 2
Identify the leading coefficient and degree, and describe the end behavior of f(x)=2x^5+4x^4-x
leading coefficient=2+
degree=5odd
describe the end behavior?
1 solutions

Answer 144184 by RAY100(1637) About Me  on 2009-04-20 13:19:20 (Show Source):
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GOOD JOB
END BEHAVIOR is fancy for what happens to function for very big or small numbers
for the ODD functions they in general slant up for positive leading coefficients
or slant down for negative leading coefficients.
This is a positive therefore it will slant up
the end on the left side will be y approaches (-infinity) as x approaches (- infinity)
the end on the right side wiil be y approaches (+ infinity) as x approaches ( + infinity)
as it is 5th degree it should have 4 turns as it goes from lower left to upper right on graph


Square-cubic-other-roots/192118: This question is from textbook Structure and Method Book 1
Sq.root of 3)(2)+ sq. root of 50
1 solutions

Answer 144183 by RAY100(1637) About Me  on 2009-04-20 13:05:26 (Show Source):
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sq rt (3*2) +sqrt (50)
sqrt 3 *sqrt2 + sqrt 25*sqrt2
(sqrt3 +5) * sqrt (2)
(5 +sqrt3 ) *sqrt2
check sqrt 6 +sqrt50 =9.52
(5+sqrt3) * sqrt2 = 9.52


Numeric_Fractions/192134: -6 +[-11 +5] / 4^2 -(-9)

i think my text book is wrong because they got 0 as an answer
is 0 the correct answer
1 solutions

Answer 144182 by RAY100(1637) About Me  on 2009-04-20 12:56:04 (Show Source):
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review original problem please
IF ( (-6) +(11-5) ) / 4^2 - (-9) or thereabouts
numerator will be zero and problem will be zero
STATED PROBLEM
(-6) + (-11+5)/4^2 -(-9)
-6+ (-6)/16 +9
3 -(3/8)
2 5/8
2.625


Functions/192136: Find the domain of the function
f(x)=
5x-1
-----
x^2-16
1 solutions

Answer 144181 by RAY100(1637) About Me  on 2009-04-20 12:44:02 (Show Source):
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f(x) =y=(5x-1)/(x^2-16)
Normally in Domain problems we seek when denominator =0
this becomes easier to see if we factor denominator
y= (5x-1) / ( x+4) (x-4)
x+4 =0, x=-4
x-4 =0, x=4
Therefore domain is all Real numbers except x= +4, or =-4


Average/192120: If f(x) = (5x-3)/(x-2)
Find the inverse function of f. would that be just the opposite? = (x-2)/(5x-3)?
State the domain of f. State the domain of the inverse function.
1 solutions

Answer 144173 by RAY100(1637) About Me  on 2009-04-20 11:36:37 (Show Source):
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INVERSE of a number is reciprocal, ie 2, inv 2 = 1/2
however inverse of FUNCTION indicates a function that is reflected over y=x
Normally this is solved by substituting x for y ,,,, and y for x
f(x) =(5x-3) / (x-2)
but f(x) =y
y = (5x-3) / (x-2) DOMAIN is all REAL numbers except x=2
inverting
x = (5y-3) / (y-2)
or (y-2) = (5y-3) /x Domain is all REAL numbers except x=0