\[f(x) = x^2y - x + 2y + 3at (1,2) \]
Partially differentiate in respect to x:
\(\frac{\partial f}{\partial x} = 2xy - 1\)
\(f_x(1,2) = 2*1*2 - 1 = 3\)
Partially differentiate in respect to x:
\(\frac{\partial f}{\partial y} = x^2 + 2\)
\(f_y(1,2) = (1)^2 + 2 = 3\)