Hi,
From the given equations in your question the solution to the value would be (0,0) as the equation of cylinder creates a surface on z = 0 and the equation of paraboloid creates a paraboloid with only one point of intersection with the cylinderical surface.
Suppose you want to solve a set of equations, you could use the following link to solve the given set of equations.
You could refer to the following link to know more about how to create equations in matlab