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starmanbrand
Registered User regular

Alright, so. I am solving inequalities and what not, and I am finding myself confused but can't find the explanation in the book.

(x-10)(x+12)>0

The solution is {X|x<-12 or x > 10}

Now. To solve this you take you use the zero property to give you the 10 > 0, which I understand.

The problem I am running into is how the x+12=0 which means x=-12 has it's inequality sign reversed.

There is only subtraction by a negative number, which you don't rotate the sign for.

Thank you, my math superiors.

(x-10)(x+12)>0

The solution is {X|x<-12 or x > 10}

Now. To solve this you take you use the zero property to give you the 10 > 0, which I understand.

The problem I am running into is how the x+12=0 which means x=-12 has it's inequality sign reversed.

There is only subtraction by a negative number, which you don't rotate the sign for.

Thank you, my math superiors.

0

This discussion has been closed.

## Posts

I don't actually recall how to solve inequalities "correctly" but that is in fact the right answer. Because if x is a negative >-12 you end up with 0 or a negative number, and if x is positive <10 you end up with 0 or a negative again. Basically if x is between -12 and 10 you'll only have a negative number on one set of parenthesis, so the answer will be negative, if x is -12 or 10 you end up with a 0 on one set of parens so the answer is 0, and if x is <-12 or >10 you end up with either 2 negatives or 2 positives which yields >0.

DaenrisonstarmanbrandonNow on your graph you need to figure out which way to shade, test (0,0) and see that you need to shade "outside" the parabola. This is the key thing, you're shading to the left of your root at x=-12, and to the right of the root at x=10.

musanmanonAwesome

starmanbrandon