\[f(x, y) = x^2y - x + 2y + 3\]
\[f_x(x, y) = 2xy - 1\] \[f_y(x, y) = x^2 + 2\]
Evaluate at (1, 2):
\[f_x(1, 2) = 2(1)(2) - 1 = 4 - 1 = 3\] \[f_y(1, 2) = 1^2 + 2 = 1 + 2 = 3\]