Question

Write the first three terms in the binomial expansion, expressing the result in simplifies form.
(x+4)^20
I know that the answer is x^20+80x^19+3040x^18, but i need an explanation on the steps of how to get it. Thanks!

Answer 1

You need to foil it out. That's how you get the answer.

(x+4)^20
=
(x+4) x (x+4)^19
= 
(x+4)^2 x (x+4)^18
etc.