Chapter 2 - The Derivative - 2.3 Introduction To Techniques Of Differentiation - Exercises Set 2.3 - Page 140: 12

\times$f'(x)=-42x^{-7}-\frac{5}{2\sqrt x}$

$f(x)=7x^{-6}-5\sqrt x=7x^{-6}-5x^{\frac{1}{2}}$ $f'(x)=7(-6)x^{-6-1}-5(\frac{1}{2})x^{\frac{1}{2}-1}$ $f'(x)=-42x^{-7}-(\frac{5}{2})x^{-\frac{1}{2}}$ $f'(x)=-42x^{-7}-\frac{5}{2\sqrt x}$