(2m-n)^2-121(m+n)^2因式分解

原式=(2m-n)²-(11m+11n)²
=[(2m-n)+(11m+11n)][(2m-n)-(11m+11n)
=-(13m+10n)(9m+12n)
=-3(13m+10n)(3m+4n)
======以下答案可供参考======
供参考答案1:
(2m-n)^2-121(m+n)^2
=[(2m-n)-11(m+n)][(2m-n)+11(m+n)]
=(2m-n-11m-11n)(2m-n+11m+11n)
=-3(3m+4n)(13m+10n)
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