Please excuse my inability to use latex, and hence the poor format of the equation.
we are given an expression with x,y,z positive integers.
the question asks that if
z= x + y/x - 1/y then prove a is a perfect square.
i figure that y/x = 1/y in order for the whole thing to be an integer but I'm not sure that this is sufficient to then go on and prove it. (Like couldn't y/x - 1/y = 1 for y>x ?)