If x is an integer and y = 3x + 2, which of the following CANNOT be a divisor of y?
i'm struggling to find the best approach to do this in 2 minutes. I started plugging in numbers but there should be a better approach. Please help. Thanks
Answer C; plugged in values of x but after a little thought which cut down the time to solve. Basically, I looked for multiples of the answer choices and if after subtracting two from these multiples, they were divisible by 3, I eliminated them.
Eg: To check for choice D, 7, I thought of a multiple of 7, that is 56; subtracted 2 to get 54; Since 54 is a multiple of 3, we can eliminate D.
Plug in x = 2 to eliminate A & E
Plug in x = 11 to eliminate B
Plug in x = 18 to eliminate D
By POE, answer = C.