If x and y are integers such that x^2=64 and y^3=64 which of the following could be true?

I. x=8
II. y= -4
III. x +y= -4

A) I only
B) II only
C) I and III only
D) II and III only
E) I, II and III

x could be –8 or 8, but y can only be 4: , not 64.

I can therefore be true. III can also be true if x = –8 and y = 4.

So the answer is C.