Question

已知 3X的平方+2XY+Y的平方+8X+8=0 求|X-Y|=?

Answer 1

3X的平方+2XY+Y的平方+8X+8=0

X^2+2XY+Y^2+2x^2+8X+8=0

(x+y)^2+2(x+2)^2=0

(x+y)^2=0

2(x+2)^2=0

x+y=0

x=-y

x+2=0

x=-2

y=-x=-(-2)=2

|X-Y|=|-2-2|=4