若x2+y2=10,xy=3,則(x-y)2=()
(x-y)2=x2+y2-2xy=10-2×3=4
若x2+y2=3,x-y=2,求xy的值和x+y的值,(x2是x的平方)
x2+y2=3即(x-y)2+2xy=3因為x-y=2,所以(x-y)2=4,4+2xy=3 xy=1/2即(x+y)2-2xy=3因為xy=1/2所以(x+y)2=4,x+y=2
x2+y2=3,xy=1,求x-y..
xy=1,2xy=2(x-y)^2=x^2-2xy+y^2=x^2+y^2-2xy=3-2=1所以x-y=1