QUESTION IMAGE
Question
the following table lists the values of functions f and g, and of their derivatives, f and g, for x = 1.
| x | f(x) | g(x) | f(x) | g(x) |
|---|
evaluate $\frac{d}{dx}f(x)cdot g(x)$ at x = 1.
Step1: Apply product - rule
The product - rule states that $\frac{d}{dx}[f(x)\cdot g(x)]=f(x)g'(x)+g(x)f'(x)$.
Step2: Substitute $x = 1$
When $x = 1$, we know from the table that $f(1)=3$, $g(1)=2$, $f'(1)=7$, and $g'(1)= - 3$.
Substitute these values into the product - rule formula:
\[
$$\begin{align*}
\frac{d}{dx}[f(x)\cdot g(x)]\big|_{x = 1}&=f(1)g'(1)+g(1)f'(1)\\
&=3\times(-3)+2\times7
\end{align*}$$
\]
Step3: Calculate the result
\[
$$\begin{align*}
3\times(-3)+2\times7&=-9 + 14\\
&=5
\end{align*}$$
\]
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$5$