x-y=3,xy=5,求代数式(7xy+4x-7y)+(6x-3xy)-(3y+4xy)的值快
问题描述:
x-y=3,xy=5,求代数式(7xy+4x-7y)+(6x-3xy)-(3y+4xy)的值
快
答
7×5+4x-7y+6x-3×5-3y+4×5=10*3=30
答
(7xy+4x-7y)+(6x-3xy)-(3y+4xy)=7xy+4x-7y+6x-3xy-3y-4xy=10x-10y=10(x-y)=10*3=30