SOLUTION: Please help! I do not understand any of this! Solve the following inequality 63x-32>63/x a.) Is the point x=0 included in the solution set of the inequality? b.) are the oth

Algebra ->  Rational-functions -> SOLUTION: Please help! I do not understand any of this! Solve the following inequality 63x-32>63/x a.) Is the point x=0 included in the solution set of the inequality? b.) are the oth      Log On


   



Question 969763: Please help! I do not understand any of this!
Solve the following inequality 63x-32>63/x
a.) Is the point x=0 included in the solution set of the inequality?
b.) are the other finite end points of the interval included in the solution set?
c.) what is the solution set? (in interval notation)

Found 2 solutions by MathLover1, Edwin McCravy:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
63x-32%3E63%2Fx...move terms containing x to one side
63x-63%2Fx%3E32...both side multiply by x
63x%2Ax-63%2Ax%2Fx%3E32%2Ax
63x%5E2-63%3E32x
63x%5E2-32x-63%3E32x-32x
63x%5E2-32x-63%3E0...factor
63x%5E2-81x%2B49x-63%3E0
%2863x%5E2-81x%29%2B%2849x-63%29%3E0
9x%287x-9%29%2B7%287x-9%29%3E0
%289x%2B7%29%287x-9%29%3E0
solutions:
if %289x%2B7%29%3E0 then x%3E-7%2F9
if %287x-9%29%3E0 then x%3E9%2F7
a.) Is the point x=0 included in the solution set of the inequality?
answer is no because we were looking for solutions (%289x%2B7%29%287x-9%29%3E0) greater then 0, second of all x is denominator in 63%2Fx,and
0 is not included EVEN if we simplify it
b.) are the other finite end points of the interval included in the solution set?
no
c.) what is the solution set? (in interval notation)
(-7%2F9,0) U (9%2F7,infinity)


Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
Although the other tutor got the right answer, she is incorrect
for multiplying both sides of the inequality by the variable x.
That's because a variable x might not be positive, and if you
multiply through by a negative, that would reverse the > to <.
Also she did not use test values on the intervals.  

Here is a correct solution:

Solve the following inequality 63x-32>63/x
63x-32%22%22%3E%22%2263%2Fx

Get 0 on the right side by subtracting 63%2Fx from both sides:

63x-32-63%2Fx%22%22%3E%22%22%220%22

Get the LCD = x on the left side:

63x%2Aexpr%28x%2Fx%29-32%2Aexpr%28x%2Fx%29-63%2Fx%22%22%3E%22%22%220%22

%2863x%5E2-32x-63%29%2Fx%22%22%3E%22%22%220%22

Factor the numerator on the left:

%28%287x-9%29%289x%2B7%29%29%2Fx%7B%7B%7B%22%22%3E%22%22%220%22

We find all the critical numbers.  They are the values
obtained by setting the numerator=0 and the denominator=0

The numerator (7x-9)(9x+7) when set equal to 0 gives 
critical numbers 9%2F7 and -7%2F9
The denominator x when set equal to 0 gives the critical
number 0.

We draw a number line and mark the critical numbers on it,
in order from smallest to largest.

-----o------o--------------------o--------------
   -7/9     0                   9/7    

We have 4 intervals to test by substituting a test point in the interval:
1. Left of -7%2F9, which is %28matrix%281%2C3%2C-infinity%2C%22%2C%22%2C-7%2F9%29%29
2. Between -7%2F9 and %220%22, which is %28matrix%281%2C3%2C-7%2F9%2C%22%2C%22%2C%220%22%29%29
3. Between %220%22 and 9%2F7, which is %28matrix%281%2C3%2C0%2C%22%2C%22%2C9%2F7%29%29
4. Right of 9%2F7, which is %28matrix%281%2C3%2C9%2F7%2C%22%2C%22%2Cinfinity%29%29

1. The easiest number in %28matrix%281%2C3%2C-infinity%2C%22%2C%22%2C-7%2F9%29%29 to test in the original is x = -1

63x-32%22%22%3E%22%2263%2Fx
63%28-1%29-32%22%22%3E%22%2263%2F%28-1%29
-63-32%22%22%3E%22%22-63 
-95%22%22%3E%22%22-63
That's false so the solution set does not include %28matrix%281%2C3%2C-infinity%2C%22%2C%22%2C-7%2F9%29%29

2. The easiest number in %28matrix%281%2C3%2C-7%2F9%2C%22%2C%22%2C0%29%29 to test in the original is x = -.1

63x-32%22%22%3E%22%2263%2Fx
63%28-.1%29-32%22%22%3E%22%2263%2F%28-.1%29
-6.3-32%22%22%3E%22%22-630 
-38.3%22%22%3E%22%22-630
That's true so the solution set does include %28matrix%281%2C3%2C-7%2F9%2C%22%2C%22%2C0%29%29

3. The easiest number in %28matrix%281%2C3%2C0%2C%22%2C%22%2C9%2F7%29%29 to test in the original is x = 1

63x-32%22%22%3E%22%2263%2Fx
63%281%29-32%22%22%3E%22%2263%2F%28-.1%29
63-32%22%22%3E%22%22-630 
31%22%22%3E%22%22-630
That's true so the solution set does include %28matrix%281%2C3%2C-7%2F9%2C%22%2C%22%2C0%29%29

3. The easiest number in %28matrix%281%2C3%2C9%2F7%2C%22%2C%22%2Cinfinity%29%29 to test in the original is x = 2

63x-32%22%22%3E%22%2263%2Fx
63%282%29-32%22%22%3E%22%2263%2F%282%29
126-32%22%22%3E%22%2231.5 
94%22%22%3E%22%2231.5
That's true so the solution set does include %28matrix%281%2C3%2C9%2F7%2C%22%2C%22%2Cinfinity%29%29

None of the critical numbers are part of the solution since the
symbol is > and not ≥.

So the solution set is:




a.) Is the point x=0 included in the solution set of the inequality?
No because if we substitute x=0,

63%280%29-32%22%22%3E%22%22cross%2863%2F0%29

It is meaningless to divide by zero.


b.) are the other finite end points of the interval included in the solution set?
No because the symbol is > and not ≥

c.) what is the solution set? (in interval notation)



Edwin