化简再求值:2(m—n)²—(m+n)(m—2n)—3n(n—m),其中m=5,n=1n=-1
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![化简再求值:2(m—n)²—(m+n)(m—2n)—3n(n—m),其中m=5,n=1n=-1](/uploads/image/z/1658662-70-2.jpg?t=%E5%8C%96%E7%AE%80%E5%86%8D%E6%B1%82%E5%80%BC%EF%BC%9A2%EF%BC%88m%E2%80%94n%EF%BC%89%26%23178%3B%E2%80%94%EF%BC%88m%2Bn%EF%BC%89%EF%BC%88m%E2%80%942n%EF%BC%89%E2%80%943n%EF%BC%88n%E2%80%94m%EF%BC%89%2C%E5%85%B6%E4%B8%ADm%3D5%2Cn%3D1n%3D-1)
化简再求值:2(m—n)²—(m+n)(m—2n)—3n(n—m),其中m=5,n=1n=-1
化简再求值:2(m—n)²—(m+n)(m—2n)—3n(n—m),其中m=5,n=1
n=-1
化简再求值:2(m—n)²—(m+n)(m—2n)—3n(n—m),其中m=5,n=1n=-1
2(m—n)²—(m+n)(m—2n)—3n(n—m),
=(m-n)(2m-2n+3n)-(m+n)(m-2n)
=(m-n)(2m+n)-(m+n)(m-2n)
=2m^2-mn-n^2-m^2+mn+2n^2
=m^2+n^2
=5^2+(-1)^2
=26
这是初中数学吧?你确定N=-1?