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.

6xy+7y+[8x-(5xy-y+6x)]
=xy+2x+8y
=5+2*1
=7