What is the product of the polynomials below?
(7x2 + 2x + 4)(2x+5)

If I expand it ,
First multiply the whole thing inside the first bracket by 2x , like,
2x * (7*2 + 2x +4) and then

Multiply the same thing by 5 , like,
5 * (7*2 + 2x + 4)

From the first you will get ,
28x + 4x^2 + 8x
From the second you will get ,
70 + 10x + 20 .

To obtain the final answer , add the two results as,
28x + 4x^2 + 8x + 70 + 10x + 20, (now add the like terms) from there you will get ,

4x^2 + 40x + 90.

Hope it helps...