计算:(2m+3n)(m-2n)=_____________________

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计算:(2m+3n)(m-2n)=_____________________计算:(2m+3n)(m-2n)=_____________________计算:(2m+3n)(m-2n)=_______

计算:(2m+3n)(m-2n)=_____________________
计算:(2m+3n)(m-2n)=_____________________

计算:(2m+3n)(m-2n)=_____________________
计算:(2m+3n)(m-2n)=【2m²-mn-6n²】

(2m+3n)(m-2n)=2m²+3mn-4mn-6n²=2m²-6n²-mn

原式=2m^2-2m×2n+3n×m-3n×2n=2m^2-mn-6n^2

2m平方-1mn-6n平方