Question

Упростите выражение:

Answer 1

$3(y+5)^2-3y^2=3cdot Big (underbrace {(y+5)^2-y^2}_{A^2-B^2}Big )=\\=[, A^2-B^2=(A-B)(A+B)]=\\=3cdot (y+5-y)(y+5+y)=3cdot 5cdot (2y+5)=15cdot (2y+5)$