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Section 3.9 : Chain Rule

14. Differentiate \(S\left( w \right) = \sqrt {7w} + {{\bf{e}}^{ - w}}\) .

Hint : Don’t get too locked into problems only requiring a single use of the Chain Rule. Sometimes separate terms will require different applications of the Chain Rule, or maybe only one of the terms will require the Chain Rule.
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For this problem each term will require a separate application of the Chain Rule and make sure you are careful with parenthesis in dealing with the root in the first term.

The derivative is then,

\[S\left( w \right) = {\left( {7w} \right)^{\frac{1}{2}}} + {{\bf{e}}^{ - w}}\hspace{0.25in}\,\, \Rightarrow \hspace{0.25in}S'\left( w \right) = \frac{1}{2}\left( 7 \right){\left( {7w} \right)^{ - \,\,\,\frac{1}{2}}} - {{\bf{e}}^{ - w}} = \require{bbox} \bbox[2pt,border:1px solid black]{{\frac{7}{2}{{\left( {7w} \right)}^{ - \,\,\,\frac{1}{2}}} - {{\bf{e}}^{ - w}}}}\]