Question

How do you get 40y from the difference of 2 squares with the problem (5y+4+3x)(5y+4-3x)? I understand distribution method. I don't know where the 40y comes from using the special product method.

Answer 1

Explanation:

(5y+4+3x)(5y+4-3x) = (5y+4)² - (3x)²......(from the difference of 2 squares )

by identity : (a+b)(a-b) = a² - b²

in this exercice ; a = 5y+4 and b = 3x