Question

find d2y/dx2 in terms of x and y if y+1/x

Answer 1

You're finding the second derivative, so to make your equation into y=x^(-1) to make it a lot easier.
All you have to do is apply the power rule: y'=nx^(n-1)
y=x^(-1) (so n would be -1)
y'=-1x^(-2)
to find the second derivative, just do the power rule again. (n=-2)
y'=-1x^(-2)
y"=2x^(-3)

Hope that helps!