Use the binomial theorem to show that 7^n + 2 is divisible by 3, where n is a positive integer.
(hint: write 7 = 6 + 1.)

By the binomial theorem,

Each term containing a factor 6 is divisible by 3, since 3 divides 6. The remaining 1 and 2 sum to 3, which is also divisible by 3.

step-by-step explanation:

the true ones are a b and d