一道data suffcient problem?

bfghdggf

For integers a and b, if (a 3 - a2 -b)1/2 = 7, what is the value of a

(1) a2 - a =12

(2) b2 -b = 2

why is the answer b?

teyvhf

1. a=4 or a=-3

2, b=2 or b=-1, but only one integer a can be deducted.

so the answer is B