confusing DS!

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confusing DS!

by rahi08 » Thu Sep 25, 2008 1:23 pm
Value of (a+b)?
1- a^2+b^2=13
2- 2b=12/a
Answer: C ?
I think it shoud be E because we get to answer for a+b
could somebody help?

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Re: confusing DS!

by Morgoth » Thu Sep 25, 2008 1:40 pm
rahi08 wrote:Value of (a+b)?
1- a^2+b^2=13
2- 2b=12/a
Answer: C ?
I think it shoud be E because we get to answer for a+b
could somebody help?
2b=12/a
ab = 6

a^2+b^2=13
a^2 + b^2 + 2ab = 13+2ab
(a+b)^2 = 13+12
(a+b)^2 = 25
(a+b) = 5

Now here I am little confused about the whole thing
if
(a+b)^2 = 25
then,
a+b = -5
or
a+b = 5
Can someone pls guide me on this. This thing keeps troubling me for some or the other reason.

When to consider both + and - for squares.

Thanks.

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by ddm » Thu Sep 25, 2008 6:07 pm
Same question as morgoth.

A+B=5 OR -5

Answer should be E?