若2m²+3mn=13,3mn+2n²=21,则4m²+15mn+6n²-44=?
题目
若2m²+3mn=13,3mn+2n²=21,则4m²+15mn+6n²-44=?
答案
4m^2+15mn+6n^2-44
=4m^2+6mn+9mn+6n^2-44
=2(2m^2+3mn)+3(3mn+2n^2)-44
=2*13+3*21-44
=26+63-44
=89-44
=45
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