Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 1 - Section 1.3 - More on Functions and Their Graphs - Exercise Set - Page 198: 85


The difference quotient for the provided function is \[-4x-2h-1\].

Work Step by Step

Consider the provided function: $f\left( x \right)=-2{{x}^{2}}-x+3$. Now, substitute $x=x+h$ in the above equation to find $f\left( x+h \right)$ That is, $\begin{align} & f\left( x+h \right)=-2{{\left( x+h \right)}^{2}}-\left( x+h \right)+3 \\ & =-2{{x}^{2}}-4xh-2{{h}^{2}}-x-h+3 \end{align}$ Now, apply the difference quotient formula, $\begin{align} & \frac{f\left( x+h \right)-f\left( x \right)}{h}=\frac{-2{{x}^{2}}-4xh-2{{h}^{2}}-x-h+3-\left( -2{{x}^{2}}-x+3 \right)}{h} \\ & =\frac{-2{{x}^{2}}-4xh-2{{h}^{2}}-x-h+3+2{{x}^{2}}+x-3}{h} \\ & =\frac{-4xh-2{{h}^{2}}-h}{h} \\ & =\frac{h\left( -4x-2h-1 \right)}{h} \end{align}$ Further solve and get, $\frac{f\left( x+h \right)-f\left( x \right)}{h}=-4x-2h-1$ Hence, the difference quotient for the provided function is $-4x-2h-1$.
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