Questions on Algebra: Expressions involving variables, substitution answered by real tutors!

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Question 170660This question is from textbook Introductory Algebra
: Solve using the elimination method.
2x - y = 6
5x + y = 22
This question is from textbook Introductory Algebra
: Solve using the elimination method.
2x - y = 6
5x + y = 22

Answer by jim_thompson5910(9897) About Me  (Show Source):
You can put this solution on YOUR website!

Start with the given system of equations:
system(2x-y=6,5x+y=22)


Add the equations together. You can do this by simply adding the two left sides and the two right sides separately like this:


(2x-1y)+(5x+y)=(6)+(22)


(2x+5x)+(-1y+1y)=6+22 Group like terms.


7x+0y=28 Combine like terms. Notice how the y terms cancel out.


7x=28 Simplify.


x=(28)/(7) Divide both sides by 7 to isolate x.


x=4 Reduce.


------------------------------------------------------------------


2x-1y=6 Now go back to the first equation.


2(4)-1y=6 Plug in x=4.


8-1y=6 Multiply.


-y=6-8 Subtract 8 from both sides.


-y=-2 Combine like terms on the right side.


y=(-2)/(-1) Divide both sides by -1 to isolate y.


y=2 Reduce.


So our answer is x=4 and y=2.


Which form the ordered pair .


This means that the system is consistent and independent.


Notice when we graph the equations, we see that they intersect at . So this visually verifies our answer.


drawing(500,500,-6,14,-8,12,<BR>
grid(1),<BR>
graph(500,500,-6,14,-8,12,(6-2x)/(-1),22-5x),<BR>
circle(4,2,0.05),<BR>
circle(4,2,0.08),<BR>
circle(4,2,0.10)<BR>
) Graph of 2x-y=6 (red) and 5x+y=22 (green)
Question 170660This question is from textbook Introductory Algebra
: Solve using the elimination method.
2x - y = 6
5x + y = 22
This question is from textbook Introductory Algebra
: Solve using the elimination method.
2x - y = 6
5x + y = 22

Answer by Mathtut(1309) About Me  (Show Source):
You can put this solution on YOUR website!
2x-y=6....eq 1
5x+y=22...eq 2
:
this problem is already set up nicely without having to multiply either equation by anything. Just add eq1 to eq 2 and the y terms will be eliminated.
:
we are left with
the x terms 2x+5x and the constants 6+22
:
2x+5x=6+22
:
7x=28
:
highlight(x=4)
now substitute x's value back into either equation....I will use eq 2
:
5(4)+y=22---->20+y=22--->subtraction 20 frome each side produces
highlight(y=2)