已知x+y=3,4xy=3.求（x-y）ˇ2的值

已知x+y=3,4xy=3.求（x-y）ˇ2的值
已知x+y=3,4xy=3.求（x-y）ˇ2的值

已知x+y=3,4xy=3.求（x-y）ˇ2的值
(x-y)^2
=x^2-2xy+y^2
=x^2+2xy+y^2-4xy
=(x+y)^2-4xy
=3^2-3
=9-3=6

根号6

(x-y)'2=x'2+y'2-2xy=(x+y)'2-4xy=9-3=6

（x-y）ˇ2=（x+y）ˇ2-4xy=9-3=6

（x-y）^2=x^2-2xy+y^2=(x+y)^2-4xy=9-3=6

（x-y)2=（x+y)2-4xy=9-3=6