高考问答excel2016裁剪图片:几道数学题
来源：百度文库 编辑：高考问答 时间：2024/05/01 17:51:20
(2x-3y)^2为何等于4x^2-12xy+9y^2
(2x-3)^2-(x+3)(x-1)为何等于3x^2-14x+12
(2x-3)^2-(x+3)(x-1)为何等于3x^2-14x+12
(2x-3y)^2
=(2x-3y)*(2x-3y)
=4x^2-6xy-6xy+9y^2=4x^2+12xy+9y^2
(2x-3)^2-(x+3)(x-1)
=（2x-3）*（2x-3）-(x+3)(x-1)
=4x^2-6x-6x+9-(x^2-x+3x-3)
=4x^2-12x+9-（x^2+2x-3)
=4x^2-12x+9-x^2-2x+3
=3x^2-14x+12
(x+y)'2=x'2+2xy+y'2