Remark
Many calculators have a key that will do this in one step. Mine is one of them. So let's start with the answer and then we'll do it the long way.
9C3 = 84. You put it into your calculator as 9 2nF nCr 3 =
Solution

3*4*7 = 84 which is what you set out to show.

Here's the solution ~




Therefore, the correct choice is A
Answer:
x= -8 x=2
Step-by-step explanation:
x^2 +6x - 6 = 10
Subtract 10 from each side
x^2 +6x -16 =0
Factor what 2 numbers multiply to -16 and add to 6
8*-2 = -16
8-2 = 6
(x+8) (x-2) =0
Using the zero product property
x+8 =0 x-2 =0
x= -8 x=2