Chapter 13 - Partial Derivatives - 13.3 Partial Derivatives - Exercises Set 13.3 - Page 936: 3

$z_x=18xy-15x^4y$ $z_y=9x^2-3x^5$

Take the first partial derivatives of the given function. When taking partial derivative with respect to x, treat y as a constant, and vice versa: $z_x=2*9x^1y-5*3x^4y=18xy-15x^4y$ $z_y=9x^2*1-3x^5*1=9x^2-3x^5$