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Find the difference quotient of \(\displaystyle f(x)=8 x^{3} + 3 x^{2} - 8 x - 9\) .
The difference quotient is \(\displaystyle \frac{f(x+h)-f(x)}{h}\). Evaluating \(\displaystyle f(x+h)=- 8 h - 8 x + 8 \left(h + x\right)^{3} + 3 \left(h + x\right)^{2} - 9\) and expanding gives \(\displaystyle f(x+h)=8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9\) Evaluating the difference quotient gives \(\displaystyle \frac{(8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9)-(8 x^{3} + 3 x^{2} - 8 x - 9)}{h}\) Simplifying gives \(\displaystyle \frac{8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h}{h}=8 h^{2} + 24 h x + 3 h + 24 x^{2} + 6 x - 8\)
\begin{question}Find the difference quotient of $f(x)=8 x^{3} + 3 x^{2} - 8 x - 9$ .
\soln{9cm}{The difference quotient is $\frac{f(x+h)-f(x)}{h}$. Evaluating $f(x+h)=- 8 h - 8 x + 8 \left(h + x\right)^{3} + 3 \left(h + x\right)^{2} - 9$ and expanding gives $f(x+h)=8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9$ Evaluating the difference quotient gives $\frac{(8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9)-(8 x^{3} + 3 x^{2} - 8 x - 9)}{h}$ Simplifying gives $\frac{8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h}{h}=8 h^{2} + 24 h x + 3 h + 24 x^{2} + 6 x - 8$ }
\end{question}
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\begin{document}\begin{question}(10pts) The question goes here!
\soln{9cm}{The solution goes here.}
\end{question}\end{document}<p> <p>Find the difference quotient of <img class="equation_image" title=" \displaystyle f(x)=8 x^{3} + 3 x^{2} - 8 x - 9 " src="/equation_images/%20%5Cdisplaystyle%20f%28x%29%3D8%20x%5E%7B3%7D%20%2B%203%20x%5E%7B2%7D%20-%208%20x%20-%209%20" alt="LaTeX: \displaystyle f(x)=8 x^{3} + 3 x^{2} - 8 x - 9 " data-equation-content=" \displaystyle f(x)=8 x^{3} + 3 x^{2} - 8 x - 9 " /> . </p> </p><p> <p>The difference quotient is <img class="equation_image" title=" \displaystyle \frac{f(x+h)-f(x)}{h} " src="/equation_images/%20%5Cdisplaystyle%20%5Cfrac%7Bf%28x%2Bh%29-f%28x%29%7D%7Bh%7D%20" alt="LaTeX: \displaystyle \frac{f(x+h)-f(x)}{h} " data-equation-content=" \displaystyle \frac{f(x+h)-f(x)}{h} " /> . Evaluating <img class="equation_image" title=" \displaystyle f(x+h)=- 8 h - 8 x + 8 \left(h + x\right)^{3} + 3 \left(h + x\right)^{2} - 9 " src="/equation_images/%20%5Cdisplaystyle%20f%28x%2Bh%29%3D-%208%20h%20-%208%20x%20%2B%208%20%5Cleft%28h%20%2B%20x%5Cright%29%5E%7B3%7D%20%2B%203%20%5Cleft%28h%20%2B%20x%5Cright%29%5E%7B2%7D%20-%209%20" alt="LaTeX: \displaystyle f(x+h)=- 8 h - 8 x + 8 \left(h + x\right)^{3} + 3 \left(h + x\right)^{2} - 9 " data-equation-content=" \displaystyle f(x+h)=- 8 h - 8 x + 8 \left(h + x\right)^{3} + 3 \left(h + x\right)^{2} - 9 " /> and expanding gives <img class="equation_image" title=" \displaystyle f(x+h)=8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9 " src="/equation_images/%20%5Cdisplaystyle%20f%28x%2Bh%29%3D8%20h%5E%7B3%7D%20%2B%2024%20h%5E%7B2%7D%20x%20%2B%203%20h%5E%7B2%7D%20%2B%2024%20h%20x%5E%7B2%7D%20%2B%206%20h%20x%20-%208%20h%20%2B%208%20x%5E%7B3%7D%20%2B%203%20x%5E%7B2%7D%20-%208%20x%20-%209%20" alt="LaTeX: \displaystyle f(x+h)=8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9 " data-equation-content=" \displaystyle f(x+h)=8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9 " /> Evaluating the difference quotient gives <img class="equation_image" title=" \displaystyle \frac{(8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9)-(8 x^{3} + 3 x^{2} - 8 x - 9)}{h} " src="/equation_images/%20%5Cdisplaystyle%20%5Cfrac%7B%288%20h%5E%7B3%7D%20%2B%2024%20h%5E%7B2%7D%20x%20%2B%203%20h%5E%7B2%7D%20%2B%2024%20h%20x%5E%7B2%7D%20%2B%206%20h%20x%20-%208%20h%20%2B%208%20x%5E%7B3%7D%20%2B%203%20x%5E%7B2%7D%20-%208%20x%20-%209%29-%288%20x%5E%7B3%7D%20%2B%203%20x%5E%7B2%7D%20-%208%20x%20-%209%29%7D%7Bh%7D%20" alt="LaTeX: \displaystyle \frac{(8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9)-(8 x^{3} + 3 x^{2} - 8 x - 9)}{h} " data-equation-content=" \displaystyle \frac{(8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h + 8 x^{3} + 3 x^{2} - 8 x - 9)-(8 x^{3} + 3 x^{2} - 8 x - 9)}{h} " /> Simplifying gives <img class="equation_image" title=" \displaystyle \frac{8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h}{h}=8 h^{2} + 24 h x + 3 h + 24 x^{2} + 6 x - 8 " src="/equation_images/%20%5Cdisplaystyle%20%5Cfrac%7B8%20h%5E%7B3%7D%20%2B%2024%20h%5E%7B2%7D%20x%20%2B%203%20h%5E%7B2%7D%20%2B%2024%20h%20x%5E%7B2%7D%20%2B%206%20h%20x%20-%208%20h%7D%7Bh%7D%3D8%20h%5E%7B2%7D%20%2B%2024%20h%20x%20%2B%203%20h%20%2B%2024%20x%5E%7B2%7D%20%2B%206%20x%20-%208%20" alt="LaTeX: \displaystyle \frac{8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h}{h}=8 h^{2} + 24 h x + 3 h + 24 x^{2} + 6 x - 8 " data-equation-content=" \displaystyle \frac{8 h^{3} + 24 h^{2} x + 3 h^{2} + 24 h x^{2} + 6 h x - 8 h}{h}=8 h^{2} + 24 h x + 3 h + 24 x^{2} + 6 x - 8 " /> </p> </p>