(x+2)^2-9=(x+2)2-32=(x+2+3)(x+2-3)=(x+5)(x-1)这个是用平方差公式，希望我写的能帮到你
(x+2+3)(x+2-3)=(x+5)(x-1)
(x+2)^2-9=(x+2+3)(x+2-3)=(x+5)(x-1)
=(X+2)^2-3^2=(X+2+3)(X+2-3)=(X+5)(X-1)
(x+5)(x-1)
