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Active Calculus 2nd Ed

Activity 1.8.4.
Consider \(f(x) = 0.1 x^2 - 1.1x + 3.4\) and \(g(x) = -0.5x^2 + 2.5x - 2\text{.}\)
(a)
Compute \(f(3)\text{,}\) \(f'(3)\text{,}\) \(g(3)\text{,}\) and \(g'(3)\text{.}\) What do you observe?
(b)
Determine \(L(x)\text{,}\) the local linear approximation to \(f(x)\) at \(x = 3\text{.}\) Explain why this function is also the local linear approximation to \(g(x)\) at \(x = 3\text{.}\)
(c)
Complete the following table of values for \(f(x)\text{,}\) \(g(x)\text{,}\) and \(L(x)\text{:}\)
Table 1.8.4. Values of \(f(x)\text{,}\) \(g(x)\text{,}\) and \(L(x)\text{.}\)
\(x\) \(2.9\) \(2.99\) \(2.999\) \(3\) \(3.001\) \(3.01\) \(3.1\)
\(f(x)\)
\(g(x)\)
\(L(x)\)
What do you notice about how \(L(x)\) approximates \(f(x)\) and \(g(x)\) near \(x = 3\text{?}\)
(d)
On the axes provided in Figure 1.8.5, plot \(f(x)\text{,}\) \(g(x)\text{,}\) and \(L(x)\) near \(x = 3\text{.}\) In addition, compute \(f''(3)\text{,}\) \(g''(3)\text{,}\) and \(L''(3)\text{.}\) How do the second derivative values and the graph explain why \(L(x)\) is a better approximation for one of the functions than it is for the other?
Figure 1.8.5. Axes for plotting \(f(x)\text{,}\) \(g(x)\text{,}\) and \(L(x)\) near \(x = 3\text{.}\)