1.(2a+3b)(3a-4b) 2.(2x-3y)(3y-2x)-(4y-3x)(3x-4y) 3.(x+3y)(x-2y)-2(x-y)平方 求这4道数学+50分

1.(2a+3b)(3a-4b)=6a^2+ab-12b^22.(2x-3y)(3y-2x)-(4y-3x)(3x-4y)=-(2x-3y)^2+(3x-4y)^2=(3x-4y+2x-3y)*(3x-4y-2x+3y)=(5x-7y)*(x-y)=5x^2-12xy+7y^23.(x+3y)(x-2y)-2(x-y)^2 =x^2+xy-6y^2-2x^2-2y^2+4xy=-x^2-8y^2+...