SOLUTION: What is/are the value/s of the inequality {{{(2x^2+6x-3)/(x^2+x-13)>=1}}} in interval notation? Thank you!

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Question 283152: What is/are the value/s of the inequality %282x%5E2%2B6x-3%29%2F%28x%5E2%2Bx-13%29%3E=1 in interval notation?
Thank you!

Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
%282x%5E2%2B6x-3%29%2F%28x%5E2%2Bx-13%29%3E=1

Subtract 1 from both sides to get 0 on the right

%282x%5E2%2B6x-3%29%2F%28x%5E2%2Bx-13%29-1%3E=0

Write 1 as 1%2F1

%282x%5E2%2B6x-3%29%2F%28x%5E2%2Bx-13%29-1%2F1%3E=0

Multiply top and bottom of 1%2F1 by LCD %28x%5E2%2Bx-13%29



%282x%5E2%2B6x-3%29%2F%28x%5E2%2Bx-13%29-%28x%5E2%2Bx-13%29%2F%28x%5E2%2Bx-13%29%3E=0

Combine the two numerators over the common denominator:

%28%282x%5E2%2B6x-3%29-%28x%5E2%2Bx-13%29%29%2F%28x%5E2%2Bx-13%29%3E=0

Remove the parentheses:

%282x%5E2%2B6x-3-x%5E2-x%2B13%29%29%2F%28x%5E2%2Bx-13%29%3E=0

Combine like terms on top:

%28x%5E2%2B5x%2B10%29%29%2F%28x%5E2%2Bx-13%29%3E=0

Find all critical values by setting numerator and
denominator = 0.

Setting numerator = 0

x%5E2%2B5x%2B10=0

discriminant = b%5E2-4%2Aa%2Ac

discriminant = 5%5E2-4%2A1%2A10=25-40=-15

discriminant is negative, so we don't
get any critical values from the numerator.

Setting denominator = 0

x%5E2%2Bx-13=0

discriminant = b%5E2-4%2Aa%2Ac

discriminant = 1%5E2-4%2A1%2A%28-13%29=1%2B52=53

So we do get critical values from the
denominator:

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+

x+=+%28-b+%2B-+sqrt%28discriminant+%29%29%2F%282%2Aa%29+

x+=+%28-1+%2B-+sqrt%2853%29%29%2F%282%2A1%29+

x+=+%28-1+%2B-+sqrt%2853%29%29%2F2+

So the two critical values are

x+=+%28-1+%2B+sqrt%2853%29%29%2F2+ and +%28-1+-+sqrt%2853%29%29%2F2+

These are approximately 3.14 and -4.14

Put these on a number line:

------o----------------------o-----
-6 -5 -4 -3 -2 -1  0  1  2  3  4  5  

Choose a whole number value left of -4.14.
for a test value.  The easiest is -5

Substitute in 
%28x%5E2%2B5x%2B10%29%2F%28x%5E2%2Bx-13%29
%28%28-5%29%5E2%2B5%28-5%29%2B10%29%2F%28%28-5%29%5E2%2B%28-5%29-13%29
%2825-25%2B10%29%2F%2825-5-13%29
10%2F%2825-5-13%29
10%2F7

That is a positive number, so we put + signs over 
that part of the number line:

 + + +
------o----------------------o-----
-6 -5 -4 -3 -2 -1  0  1  2  3  4  5

Next choose a whole number value between the
two critical points for a test value.  The 
easiest is 0

Substitute in 
%28x%5E2%2B5x%2B10%29%2F%28x%5E2%2Bx-13%29
%28%280%29%5E2%2B5%280%29%2B10%29%2F%28%280%29%5E2%2B%280%29-13%29
10%2F%28-13%29
10%2F%28-13%29
-10%2F13

That is negative so we put - signs over that part 
of the number line:

 + + +  - - - - - - - - - - 
------o----------------------o-----
-6 -5 -4 -3 -2 -1  0  1  2  3  4  5

Choose a whole number value right of 3.14.
for a test value.  The easiest is 4

Substitute in 
%28x%5E2%2B5x%2B10%29%2F%28x%5E2%2Bx-13%29
%28%284%29%5E2%2B5%284%29%2B10%29%2F%28%284%29%5E2%2B%284%29-13%29
%2816-20%2B10%29%2F%2816%2B4-13%29
6%2F7

That is a positive number, so we put + signs over 
that part of the number line:

 + + +  - - - - - - - - - -    + + +
------o----------------------o------
-6 -5 -4 -3 -2 -1  0  1  2  3  4  5

Since the inequality of 

%28x%5E2%2B5x%2B10%29%29%2F%28x%5E2%2Bx-13%29%3E=0

is %22%22%3E=0

we choose the intervals with + signs.

We cannot include the end points themselves

because they cause the denominator to be 0.

So the solution set is

(-infinity,%28-1+-+sqrt%2853%29%29%2F2) U (%28-1+%2B+sqrt%2853%29%29%2F2+, infinity)

Edwin