∵4m+n=90,2m-3n=10,
∴(m+2n)2-(3m-n)2
=[(m+2n)+(3m-n)][(m+2n)-(3m-n)]
=(4m+n)(3n-2m)
=-900.
已知4m+n=90,2m-3n=10,求(m+2n)2-(3m-n)2的值.
已知4m+n=90,2m-3n=10,求(m+2n)2-(3m-n)2的值.
数学人气:291 ℃时间:2019-08-26 06:54:23
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