Question

用平方差公式计算（x+2y-3)(x-2y-3)

解方程x-1分之x-1=(x-1)(x+2)分之3

Answer 1

看吵搭成 （x-3+2y）（x-3-2y）指旅
=（x-3）^2 - 4y^2
= x^2-6x+9-4y^2
( x^2 是x的平方的意思升逗拿 )

Answer 2

x=1

Answer 3

x^2-6x+9-4y^2
1

Answer 4

（x-3+2y)(x-3-2y)=(x-3)^2-(2y)^2=x^2-6x+9-4y^2