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

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

计算 (2m+n-3)(2m-n-3) 计算 :(2m+n-3)(2m-n-3)
把第一个括号中的每一项分别乘进第二个括号中:
(2m+n-3)(2m-n-3)=2m*2m-2m*n-2m*3+n*2m-n*n-n*3-3*2m+3n+9
=4m^2-2mn-6m+2mn-n^2-3n-6m+3n+9
=4m^2-n^2-12m+9

(2m+n-3)(2m-n-3)
=(2m-3+n)(2m-3-n)
=(2m-3)^2-n^2
=4m^2-12m+9-n^2
=4m^2-12m-n^2+9
这算是最简单的算法了