已知x^2-xy=10,xy-y^2=20,求: x^2-y^2 x^-2xy+y^2
∵x^2-xy=10
∵xy-y^2=20
∴(x^2-xy)+(xy-y^2)=30
∴x^2-y^2=30
∵x^2-xy=10
∵xy-y^2=20
∴(x^2-xy)-(xy-y^2)=x^-2xy+y^2=-10
∴x^-2xy+y^2=-10
已知x-xy=20,xy-y=-12,則x-y=?
加起來就好了啊x-xy+(xy-y)=20+(-12)
x-y=8
(1/y-1/x)乘(xy)/(x^2-2xy+y^2)怎麼化簡
(1/y-1/x)*(xy)/(x^2-2xy+y^2)=(X-y)/(x-y)^2 =1/(x-y)