Question

化简xy(x^-2+y^-2),并求x=2.y=3是的值

Answer 1

xy(x^-2+y^-2)=xy(1/x² + 1/y²)=xy*(x²+y²)/(x²y²)=(x²+y²)/(xy)

所以当x=2,y=3时,原式=(4+9)/(2*3)=13/6