Francisco P. answered 11/30/14
Tutor
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Well-Versed in Calculus
Auburn,
When you take partial derivatives with respect to one variable, treat the others as if they were constants.
We are given f(x,y) = x/y and we are to find the partial derivatives.
Since there are two variables, we take two partial derivatives: one with respect to x, the other with respect to y.
fx(x,y) = (∂/∂x)(x/y) = 1/y
fy(x,y)= (∂/∂y)(x/y) = -x/y2
Now just substitute to get the values of the partial derivatives at (1,2).
Geaux Tigers!