Question

simplify
$(6a + 5b + 4c) ^{2} - (6a - 5b - 4c) ^{2}$

Answer 1

(a+b+c)²= a²+b²+c²+2ab+2bc+2ac
(6a+5b+4c)²=36a²+25b²+16c²+60ab+40bc+48ac
(6a-5b-4c)²= 36a²+25b²+16c²-60ab+40bc-48ac

(6a+5b+4c)² - (6a-5b-4c)²
=36a²+25b²+16c²+60ab+40bc+48ac-36a²-25b²-16c²+60ab-40bc+48ac
=120ab+96ac
=24(5ab+4ac)