Can some one please explain how this equation works? Thanks

The first term:

(1/x^-1)^-1      = (  1/(1/x)  )^-1     1/ (1/x) =  x   so this simplifies to  x^-1   which equals   1/x

 

The second term:

(x^-1 + y^-1)  =   ( 1/x + 1/y)

 

Now Multiply them together

 

1/x (1/x + 1/y) =  1/ (x^2) + 1/(xy)