please solve showing steps

Consider the function is U(x.y) =-1.2/x - 3.8/y and a move along any level curve of this function where x>0 and y>0. What is the value of the derivative which we can use to determine whether such level curves are concave or convex at the point were x=3.8 and y=3.2? Remember to enter the number in decimal form. If the number is negative, then use the negative sign (e.g., -3.298)