Question

for odd "N" Prove that 3^n +7^n is divisible by 10

Answer 1

if n is odd, then it can be factored

(3+7)(3^(n-1) - 7*3^(n-2) ... + 7^(n-1))

Answer 2

huh?

Answer 3

Do you know that
a^n + b^n = (a+b) (a^(n-1) - ba^(n-2) ... + b^(n-1)

Answer 4

nope, wait where is this rule from, cause the question i am doing atm is an induction question and i haven't seen such a rule

Answer 5

then do you know that a^n - b^n = (a-b)(a^(n-1)... +b^(n-1)

Answer 6

are you sure this works ....?

Answer 7

a^n + b^n = (a+b) (a^(n-1) - ba^(n-2) ... + b^(n-1))
works if n is odd.

Answer 8

Virtus, are you working on congruences?