(2m-n)(n-2m)-(n-m)²要过程

(2m-n)(n-2m)-(n-m)²要过程
(2m-n)(n-2m)-(n-m)²
要过程

(2m-n)(n-2m)-(n-m)²要过程
(2m-n)(n-2m)-(n-m)²
=2mn-n²-4m²+2mn-n²+2mn-m²
=6mn-2n²-5m²

(2m-n)(n-2m)-(n-m)²
=-（4m^2-n^2）- (n-m)²
=n^2-4m^2-m^2-n^2+2mn
=2mn-5m^2

=-（4m^2-n^2）- (n-m)²
=n^2-4m^2-m^2-n^2+2mn
=2mn-5m^2

(2m-n)(n-2m)-(n-m)²=-（n-2m)²-(n-m)²
=-n²-4m²+4mn-n²+2mn-m²
=6mn-2n²-5m²