Answer:
D (x-10)
Step-by-step explanation:
x^2 - 8x - 20
(x -10)(x+2)
1. You need to multiply the denominator by something that will make the content of the radical be a square—so that when you take the square root, you get something rational. Easiest and best is to multiply by √6. Of course, you must multiply the numerator by the same thing. Then simplify.

2. Identify the squares under the radical and remove them.

The answer is A because the equation is 40/10 which would give you 4 and it asks m/s.