# Thread: Sign Chart - Critical Value Method

1. ## Sign Chart - Critical Value Method

Dear Forum I am trying to figure out the following , but I am having no luck, please help if possible

Solve x^2 + 11x + 18 > 0 using the Critical Value (Sign Chart) method.

Thanks -AC-

2. Originally Posted by AlgebraicallyChallenged
Dear Forum I am trying to figure out the following , but I am having no luck, please help if possible

Solve x^2 + 11x + 18 > 0 using the Critical Value (Sign Chart) method.

Thanks -AC-
First, factor your inequality to get:

$\displaystyle (x+9)(x+2) > 0$

-9 & -2 are your critical values, so put those on your sign chart.
Then to the right of the chart, write your two factors. Choose values in the intervals between each and write the sign for each.
You should have:
- two negatives for the interval from $\displaystyle (-\infty, -9)$ => +

- a positive and a negative for the interval from $\displaystyle (-9,-2)$ => -

- two positives for the interval from $\displaystyle (-2,\infty)$ => +

So, the question is asking you:
Where is $\displaystyle x^2 + 11x +18$ GREATER than zero?

So your answer is: $\displaystyle (-\infty,-9) U (-2,\infty)$