Well, this one seems to be straightforward, but there are

Question

Well, this one seems to be straightforward, but there are some doubts....

Sergey_is_cool · Answer

you need both statements to solve this one. 
2 equations 2 unknowns

nick_sun · Answer

But why cannot we guess the values from st1? We've got two sqrds, the difference between which is 16, the first sqrd is greater than the second one: 5^2 - 3^2 = 16. Are there any other sqrds the difference between which can give us 16?

KillerSquirrel · Answer

I would say (C)

a^4-b^4 = (a^2-b^2)(a^2+b^2)

Statement 1

(a^2-b^2)=16

we can plug in but we are still missing (a^2+b^2)

insufficient

Statement 2

(a+b)=8

we are still missing (a^2+b^2)

insufficient

Statement 1&2

Knowing that (a^2-b^2)=(a-b)(a+b)=16

and (a+b)=8

we can plug in and find that (a-b)*8=16

a-b=2 & a+b=8

2b=6

b=3

a=5

so the answer is (C)

:-D

Sergey_is_cool · Answer

yeah but you can't just guess numbers you have to have the way to prove that the the equation has only one solution.(It's my guess) Do you have the answer?

KillerSquirrel · Answer

please note that a & b don't have to be integers !!!!!

Well, this one seems to be straightforward, but there are

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards