What is the minimum value of the expression x^2 + y^2 - 6x + 4y + 18 for real x and y ?
Taking the derivative with respect to x and y, we get that the minimum value occurs at x = 6 and y = -4. This gives us a minimum value of 6^2 + (-4)^2 - 6*6 + 4*(-4) + 18.
x=3, y=-2
