Question

已知X+Y=8,XY=12,求值X-Y

Answer 1

这个很好算，因为X+Y=8，所以X=8-Y,则Y（8-Y)=12，可得Y^2-8Y+12=0
可得Y=2或者Y=6
Y=2时，X=6
Y=6时，X=2
则X-Y=-4或者X-Y=4。

Answer 2

X+Y=8 (1)
XY=12 (2)
(1)^2-4*(2)
x^2-2xy+y^2=64-48
(x-y)^2=16
x-y=±4
希望能帮到你，祝学习进步O(∩_∩)O

Answer 3

X+Y=8
(X+Y)^2=64
X^2+2XY+Y^2=74
X^2+24+Y^2=40
X^2+Y^2=40
X^2+Y^2-2XY=40-2XY
(X-Y)^2=40-24
(X-Y)^2=16
X-Y=+-4

Answer 4

∵X+Y=8,XY=12
∴X-Y=√￣（X+Y）2－4XY￣
=√￣64－48￣
=4
即：X-Y=4

Answer 5

(x+y)^2-4xy=(x-y)^2;
所以x-y=4或-4

Answer 6

X-Y=-4或X-Y=4