已知丨x+3丨+丨y-x+4丨=0,求(x-y)(x+y)的值 越快分越多.
问题描述:
已知丨x+3丨+丨y-x+4丨=0,求(x-y)(x+y)的值 越快分越多.
答
丨x+3丨+丨y-x+4丨=0
丨x+3丨=丨y-x+4丨=0
x+3=0,y-x+4=0
x=-3,y=-7
(x-y)(x+y)=4*(-10)=-40