数学题=y(y+3)-4(y+3)2=(y+3)(y-4y-12)
问题描述：
数学题=y(y+3)-4(y+3)2=(y+3)(y-4y-12)
答
(y+3)^2/8-y=(y+3)/4-(y-1)/2
各项都乘以8,得
(y+3)^2-8y=2(y+3)-4(y-1)
y^2-2y+9=-2y+10
y^2=1
y1=-1 y2=1