MathRevolution wrote:

If a and b are positive integers, is ab an even?

1) (a+1)b=even

2) (a+1)^b=odd

*An answer will be posted in 2 days.

is \(ab\) an even ?

which mean only \(a\) or only \(b\) or both \(a\) and \(b\) are even.

1) \((a+1)b\) = even, which can mean, \(b\) alone is even or \(a\) alone is odd or both \(b\) is even and \(a\) is odd. Not sufficient. Eliminate A and D

2) \((a+1)^b\) = odd, which means no matter what \(b\) is , \(a\) has to be even. Sufficient.

Answer is B.