Please help due today

F(n + 1) = f(n) – 8. if f(1) = 100, what is f(6)?

If y varies directly as x2 and y=6 when x=6, find the constant of variation.

Me! i really need to get this right before 9. prove the divisibility of 7^6+7^5-7^4 by 11. use factoring so you get a number times 11. just tell me the number. i need this done asap