If a and b are positive integers, and a=4b+16, the greatest common divisor of a and b CANNOT be Select.
A) 2 B) 9 C) 4 D) 8 E) 16
If b is 2, 4, 8, or 16, then GCD of a and b is 2, 4, 8, and 16 respectively. So, by POE the answer must be B.   Still: if b is a multiple of 9, then a is 16 greater than a multiple of 9, so not a multiple of 9, so both of them cannot be divisive by 9.   Answer: 9.
<result>B</result>
If a and b are positive integers, and a=4b+16, the greatest common divisor of a and b CANNOT be