先化简,再求值.6.如果m-3n+1=0,求4﹙m-3n﹚²-m+3n-5﹙m-3n﹚²-7的值
问题描述:
先化简,再求值.6.如果m-3n+1=0,求4﹙m-3n﹚²-m+3n-5﹙m-3n﹚²-7的值
答
∵m-3n+1=0
∴m-3n=-1
4﹙m-3n﹚²-m+3n-5﹙m-3n﹚²-7
=4﹙m-3n﹚²-(m-3n)-5﹙m-3n﹚²-7
=-(m-3n)²-(m-3n)-7
=-(-1)²-(-1)-7
=-1+1-7
=-7