怎么计算:1.(x-2y+z)(-x+2y+z) 2.(2x-3y-1)(2x+3y-1)
问题描述:
怎么计算:1.(x-2y+z)(-x+2y+z) 2.(2x-3y-1)(2x+3y-1)
答
原式=(z+x-2y)(z-x+2y)=z^2-(x-2y)^2=z^2-x^2+4xy-4y^2
原式=(2x-1-3y)(2x-1+3y)=(2x-1)^2-9y^2=4x^2-4x-9y^2+1
答
(x-2y+z)(-x+2y+z)=(z+x-2y)(z-(x-2y))=z^2-(x-2y)^2=z^2-x^2+4xy-4y^2(2x+3y-1)(2x-3y+1)=[2x+(3y-1)][2x-(3y-1)]=(2x)^2-(3y-1)^2=4x^2-(9y^2-6y+1)=4x^2-9y^2+6y-1