Question

I have a general notation question about a partial derivative.. Find the second order derivative r subscript xy for r(x,y)=xy/(5x+7y)

Answer 1

[70*x*y]/{[5*x]+[7*y]}^3

Answer 2

I know thats the answer, my question is Does r(x,y) mean to multiply the x and y term?

Answer 3

first u have to differentiate r with respect to y by keeping x as const and then the result u have to differentiate with x in which y will be constant.