SOLUTION: solve : {{{x^2(x+8)<0}}}

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Question 247645: solve :
Answer by RicaMath(8)   (Show Source): You can put this solution on YOUR website!
Here, we see two numbers are being multiplied together in the inequality ( and ). And we know that the only way to multiply two numbers together and get a number less than 0 is to multiply a positive and a negative number together. (positive * positive = positive; and negative * negative = positive)


Thus, we know that is true in either of the following situations:


1. and
2. and


If you look at the first statement carefully, you may note that it can never be true. As previously stated, positive * positive = positive; and negative * negative = positive, so there is no way you can take any integer, square it, and get a negative number. This means, we only need to concern ourselves with the second situation, and .
So, let's solve the two inequalities:

(get the square root of both sides)





So, we get as our answer. (because all items > -8 are also > 0, so we use the more restrictive option as our final answer to ensure all possibilities work.)


We can always double check our work. Let's take , as that satisfies our answer condition. Plugging it into our original inequality:


, which is a true statement.

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