计算:1.[(m+n)(n-m)-(m+n)^2+3m(m+n)]除以(-2M),其中m=-4,n=2 2.(x+y)(-x+y)-(x-y)^2-(X^2y-xy^2)除
问题描述:
计算:1.[(m+n)(n-m)-(m+n)^2+3m(m+n)]除以(-2M),其中m=-4,n=2 2.(x+y)(-x+y)-(x-y)^2-(X^2y-xy^2)除
答
1.[(m+n)(n-m)-(m+n)^2+3m(m+n)]÷(-2m)
=(m+n)[(n-m)-(m+n)+3m]÷(-2m)
=(m+n)(n-m-m-n+3m)÷(-2m)
=m(m+n)÷(-2m)
=-(m+n)/2
=-(-4+2)/2
=1