D. All other choices are wrong
Answer: The slope is -2. Hope this helps :)
Step-by-step explanation:
y2 - y1/ x2 - x1
Not sure on the equation but you could try drawing a probability tree

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. 