hi guys,

can anyone help me to find my mistake, I can't figure out what's wrong, probably something small.

the correct answer should be -5<=x<=4

I got -1<=x<=4

cheers !

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- Nov 16th 2010, 01:40 AMWeeGsqrt(x + 5) - sqrt(8 - x) < 1: Need help to find my mistake
hi guys,

can anyone help me to find my mistake, I can't figure out what's wrong, probably something small.

the correct answer should be -5<=x<=4

I got -1<=x<=4

cheers ! - Nov 16th 2010, 04:54 AMHallsofIvy
It's not so much a matter of a single "mistake" as that your whole concept is wrong! Do you understand that if x< y it does

**not**necessarily follow that $\displaystyle x^2< y^2$? -3< 2 but 9 is NOT less than 4.

I would do this instead: solve the**equation**$\displaystyle \sqrt{x+ 5}- \sqrt{8- x}= 1$. Those points separate "<" and ">". Check one point in each interval to see if the the inequality is satisfied in that interval.