Question

设函数f(x,y)=xy/(x^2+y^2),则f(y/x,1)=

Answer 1

f(x,y)=xy/(x^2+y^2)

则f(y/x,1)
=(y/x)*1/[(y/x)^2+1^2]
=y/[x*(y^2/x^2+1)]
=y/(y^2/x+x)
=xy/(x^2+y^2)

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