Chapter 14: Partial Derivatives - Section 14.3 - Partial Derivatives - Exercises 14.3 - Page 807: 5

$f_x=2(xy-1)\times y$ $f_y=2(xy-1)\times x$

Take the first partial derivatives of the given function. When taking a partial derivative with respect to x, treat y as a constant, and vice versa: $f_x=2(xy-1)\times y$ $f_y=2(xy-1)\times x$