x2 + y2 vs (x +y)2

[rohit_gmat]

Is x^2 + y^2 > 100 ?

1) 2xy < 100

2) (x + y)^2 > 200

OAC

I plugged in numbers. Anyone can explain why B is wrong? I tried plugging in.. is it the best method here? Any set of numbers that will prove it insufficient?

Thanks

[Brent@GMATPrepNow]

Is x^2 + y^2 > 100 ?

1) 2xy < 100

2) (x + y)^2 > 200

OAC

I plugged in numbers. Anyone can explain why B is wrong? I tried plugging in.. is it the best method here? Any set of numbers that will prove it insufficient?

Thanks

You are correct, the OA for that question is actually B.

Please see: https://www.beatthegmat.com/x2-y2-t92678.html

Cheers,
Brent