If x and y are positive integers, and y=x^2+8, the greatest common divisor of a and b CANNOT be  Select
A) 9	B) 1	C) 2	D) 4	E) 8
If x is 1, 2, 4, or 8, then GCD of x and y is 1, 2, 4, and 8 respectively. So, by POE the answer must be A.   Still: if x is a multiple of 9, then y is 8 greater than a multiple of 9, so not a multiple of 9, so both of them cannot be divisive by 9.   9nswer: 9.
<result>A</result>
If x and y are positive integers, and y=x^2+8, the greatest common divisor of a and b CANNOT be