已知m^2-mn=2,mn-n^2=5则3m^2+2mn-5n^2

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已知m^2-mn=2,mn-n^2=5则3m^2+2mn-5n^2已知m^2-mn=2,mn-n^2=5则3m^2+2mn-5n^2已知m^2-mn=2,mn-n^2=5则3m^2+2mn-5n^2应

已知m^2-mn=2,mn-n^2=5则3m^2+2mn-5n^2
已知m^2-mn=2,mn-n^2=5则3m^2+2mn-5n^2

已知m^2-mn=2,mn-n^2=5则3m^2+2mn-5n^2
应该是3m^2+2mn-5n^2=3(m²-mn)+5(mn-n²)=3×2+5×5=6+25=31吧!希望对你有用

31 吧

m^2-mn=2, mn-n^2=5
3m^2+2mn-5n^2=3(m^2-mn)+5(mn-n^2)=3*2+5*5=31.

3m^2+2mn-5n^2=3(m²-mn)+5(mn-n²)=3×2+5×5=6+25=31