What is the coefficient of x^2 in (x^3 + x^2 + x + 1)(x^4 + 3x^3 + 8x + 7x + 1)?
I will assume you meant THIS:
(x^3 + x^2 + x + 1)(x^4 + 3x^3 + 8x^2 + 7x + 1)
When you multiply the two polynomials you will get these parts :
x^2 * 1 + x * 7x + 1 * 8x^2 = 16 x^2
So the coefficient will be ' 16 '