若x^2+4x+y^2-6Y+13=0,则(x+2y)(x-2y)的值
问题描述:
若x^2+4x+y^2-6Y+13=0,则(x+2y)(x-2y)的值
答
x^2+4x+y^2-6Y+13=0
(x+2)^2+(y-6)^2=0
x=-2 y=6
(x+2y)(x-2y)
=x^2-4y^2
=4-144
=-140