已知x＋y=3,xy=-10,求﹙1﹚x^2－xy＋y^2;﹙2﹚x－y的绝对值.

已知x＋y=3,xy=-10,求﹙1﹚x^2－xy＋y^2;﹙2﹚x－y的绝对值.
已知x＋y=3,xy=-10,求﹙1﹚x^2－xy＋y^2;﹙2﹚x－y的绝对值.

已知x＋y=3,xy=-10,求﹙1﹚x^2－xy＋y^2;﹙2﹚x－y的绝对值.
x^2－xy＋y^2
=（x+y）²-3xy
=9+30
=39
（x－y）²
=（x+y）²-4xy
=9+40
=49
Ix-yI
=7

x^2－xy＋y^2
=（x+y）²-3xy
=9+30
=39
（x－y）²
=（x+y）²-4xy
=9+40
=49
Ix-yI
=7

(1)x²-xy+y²
=(x+y)²-3xy
=9+30
=39
(2)(x-y)²
=(x+y)²-4xy
=9+40
=49
所以丨x-y丨=7