Question

Fiind and evaluate each at the given point.

f(x, y) &= \frac{x y}{x-y}, \text{ at point } (9, -9) \\
f_x(x, y) &= -\frac{y}{x-y'} \\
f_{y'}(x, y) &= \frac{x}

Answer 1

To evaluate f(x, y) at the given point (9, -9), substitute x = 9 and y = -9 into the function f(x, y) = xy/(x-y), resulting in f(9, -9) = -81.

Step-by-step explanation:

To find and evaluate f(x, y) at the given point (9, -9), we substitute the given values into the function. The function is f(x, y) = \frac{{xy}}{{x-y}}. So, when we substitute x = 9 and y = -9 into the function, we get f(9, -9) = \frac{{9(-9)}}{{9-(-9)}}.

Simplifying this expression, we have f(9, -9) = -81.