Chapter 12.3 Exercise 6 \[ \begin{aligned} f(x,y)&=x^3 -3x + y^2 -6y \\at (1,2) \end {aligned} \] Partial derivaties with respect to x \[ \begin{aligned} f(x,y)&=x^3 -3x + y^2 -6y \\\frac{\partial f}{\partial x} &=3x^2 -3 = 3*0 -3 =0 \end {aligned} \] Partial derivaties with respect to y \[ \begin{aligned} f(x,y)&=x^3 -3x + y^2 -6y \\\frac{\partial f}{\partial y} &=2y-6 = 2*2 -6 = -2 \end {aligned} \]