Find the Partial Derivative $f(5,-6)$ When $f(x, y)=7 x^{2}-9 x y$
A) 129
B) -54
C) -45
D) 39

Find the partial derivative.
-Find $f(5,-6)$ when $f(x, y) =7 x^{2}-9 x y$ .

A) 129
B) -54
C) -45
D) 39