求6xy+7y+[8x-(5xy-y+6x)]的值,其中x+4y=1,xy=5.
问题描述:
求6xy+7y+[8x-(5xy-y+6x)]的值,其中x+4y=1,xy=5.
答
6xy+7y+[8x-(5xy-y+6x)]
=xy+2x+8y
=5+2*1
=7