Answer:
24
Step-by-step explanation:
If you use Pascal's triangle, which I did, you will look at the 5th row of the triangle which contains the numbers 1, 4, 6, 4, 1
If we expand using a = 2x and b = -1, then the expansion looks like this:
If you simplify all that down by multiplying, you'll get
If you don't know how to use Pascal's triangle, you need to learn. It's so very cool!