(y-3)^2-16y^2=?(Подробно только)

Question

(y-3)^2-16y^2=?(Подробно только)

Answer 1

A² -b² =(a -b)(a +b)

пусть y-3 =a, тогда
a² -16у² =(a -4y)(a +4y) = (y -3 -4y)(y -3 +4y) = (-3 -3y)(-3 +5y) = -3(1 +y)(5y -3)

или
(y -3)² -16y² = (y-3 -4y)(y-3 +4y) =(-3 -3y)(-3+5y) = -3(1 +y)(5y -3)