Answer:
the first one.
Step-by-step explanation:
The answer is B 3x^4-13x^3-x^2-11x+6

Formula works when n=1
Assume the formula also works, when n=k.
Prove that the formula works, when n=k+1

Since the formula has been proven with n=1 and n=k+1, it is true. 
Answer:
45$ per house cleaned
Step-by-step explanation:
135$ / 3 houses = 45
225$/ 5 houses = 45