4.6 Assess Your Understanding

Skill Building

In Problems 1–42, use calculus to graph each function. Follow the steps for graphing a function.

Question

\(f(x) =x^{4}-6x^{2}+10\)

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\(f(x) =x^{5}-3x^{3}+4\)

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\(f(x)=\dfrac{1}{x-2}\)

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\(f(x)=\dfrac{2}{x+2}\)

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\(f(x)=\dfrac{2}{x^{2}-4}\)

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\(f(x)=\dfrac{1}{x^{2}-1}\)

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\(f(x)=\dfrac{2x-1}{x+1}\)

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\(f(x)=\dfrac{x-2}{x}\)

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\(f(x)=\dfrac{x}{x^{2}+1}\)

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\(f(x)=\dfrac{2x}{x^{2}-4}\)

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\(f(x)=\dfrac{x^{2}+1}{2x}\)

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\(f(x)=\dfrac{x^{2}-1}{2x}\)

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\(f(x)=\dfrac{x^{4}+1}{x^{2}}\)

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\(f(x)=\dfrac{x^{3}+1}{x+1}\)

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\(xy=x^{2}+2\)

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\(xy=x^{2}+x-1\)

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\(f(x)=\dfrac{x^{2}}{x+3}\)

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\(f(x)=\dfrac{3x^{2}-1}{x-1}\)

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\(f(x)=1+\dfrac{1}{x}+\dfrac{1}{x^{2}}\)

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\(f(x)=\dfrac{2}{x}+\dfrac{1}{x^{2}}\)

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\(f(x)=\sqrt{3-x}\)

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\(f(x)=x\sqrt{x+2}\)

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\(f(x)=x+\sqrt{x}\)

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\(f(x)=\sqrt{x}-\sqrt{x+1}\)

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\(f(x)=\dfrac{x^{2}}{\sqrt{x+1}}\)

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\(f(x)=\dfrac{x}{\sqrt{x^{2}+2}}\)

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\(f(x)=\dfrac{1}{({x+1})({x-2})}\)

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\(f(x)=\dfrac{1}{({x-1})({x+3})}\)

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\(f(x)=x^{2/3}+3x^{1/3}+2\)

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\(f(x)=x^{5/3}-5x^{2/3}\)

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\(f(x)=\sin x-\cos x\)

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\(f(x)=\sin x+\tan x\)

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\(f(x)=\sin ^{2}x-\cos x\)

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\(f(x)=\cos ^{2}x+\sin x\)

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\(y=\ln x-x\)

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\(y=x\, \ln x\)

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\(f(x)=\ln (4-x^{2})\)

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\(y=\ln (x^{2}+2)\)

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\(f(x)=3e^{3x}( 5-x)\)

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\(f(x)=3e^{-3x}( x-4)\)

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\(f(x)=e^{-x^{2}}\)

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\(f(x)=e^{1/x}\)

Applications and Extensions

In Problems 43–52, for each function:

  1. Use a CAS to graph the function.
  2. Identify any asymptotes.
  3. Use the graph to identify intervals on which the function increases or decreases and the intervals where the function is concave up or down.
  4. Approximate the local extreme values using the graph.
  5. Compare the approximate local maxima and local minima to the exact local extrema found by using calculus.
  6. Approximate any inflection points using the graph.

Question

\(f(x)=\dfrac{x^{2/3}}{x-1}\)

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\(f(x)=\dfrac{5-x}{x^{2}+3x+4}\)

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\(f(x)=x+\sin (2x)\)

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\(f(x)=x-\cos x\)

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\(f(x)=\ln (x\sqrt{x-1})\)

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\(f(x)=\ln (\tan ^{2}x)\)

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\(f(x)=\sqrt[3]{\sin x}\)

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\(f(x)=e^{-x}\cos x\)

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\(y^{2}=x^{2}( 6-x)\), \(y\geq 0\)

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\(y^{2}=x^{2}(4-x^{2}),\) \(y\geq 0\)

318

In Problems 53–56, graph a function \(f\) that is continuous on the interval \([1,6]\) and satisfies the given conditions.

Question

\( \begin{array}[t]{l} f^\prime (2)\hbox{ does not exist}\\ f^\prime (3)=-1\\ f^{\prime \prime} (3)=0\\ f^\prime (5)=0 \\ f^{\prime \prime} (x)<0,\quad 2<x<3\\ f^{\prime \prime} (x)>0,\quad x>3 \end{array}\)

Question

\( \begin{array}[t]{l} f^\prime (2)=0 \\ f^{\prime \prime} (2)=0 \\ f^\prime (3)\hbox{ does not exist} \\ f^\prime (5)=0 \\ f^{\prime \prime} (x)>0,\quad 2<x<3 \\ f^{\prime \prime} (x)>0,\quad x>3 \end{array}\)

Question

\( \begin{array}[t]{l} f^\prime (2)=0 \\ \lim\limits_{x\rightarrow 3^{-}}\,f^\prime (x)=\infty \\ \lim\limits_{x\rightarrow 3^{+}}\,f^\prime (x)=\infty \\ f^\prime (5)=0 \\ f^{\prime \prime} (x)>0, \quad x<3 \\ f^{\prime \prime} (x)<0, \quad x>3 \end{array}\)

Question

\( \begin{array}[t]{l} f^\prime (2)=0 \\ \lim\limits_{x\rightarrow 3^{-}}\,f^\prime (x)=-\infty \\ \lim\limits_{x\rightarrow 3^{+}}{\,}f^\prime (x)=-\infty \\ f^\prime (5)=0 \\ f^{\prime \prime} (x)<0,\quad x<3 \\ f^{\prime \prime} (x)>0, \quad x>3 \end{array}\)

Question

Sketch the graph of a function \(f\) defined and continuous for \(-1\leq x\leq 2\) that satisfies the following conditions: \[ \begin{array}{@{\hspace*{-1.7pc}}l} f(-1)= 1 \quad f(1) = 2 \quad f(2) = 3 \quad f(0) = 0 \quad f \left( {\dfrac{1}{2}}\right) =3\\[3pt] \quad \lim\limits_{x\rightarrow -1^{+}}f^\prime (x) =-\infty\quad \lim\limits_{x\rightarrow 1^{-}} f^\prime (x) = -1 \quad \lim\limits_{x\rightarrow 1^{+}} f^\prime (x)=\infty\\ {f\hbox{ has a local minimum at }0} \quad {f\hbox{ has a local maximum at }\dfrac{1}{2}} \end{array} \]

Question

Graph of a Function Which of the following is true about the graph of \(y=\ln |x^{2}-1|\) in the interval \((-1,1)\)?

  1. The graph is increasing.
  2. The graph has a local minimum at \((0,0).\)
  3. The graph has a range of all real numbers.
  4. The graph is concave down.
  5. The graph has an asymptote \(x=0.\)

Question

Properties of a Function Suppose \(f(x)=\dfrac{1}{x}+\ln x\) is defined only on the closed interval \(\dfrac{1}{e}\leq x\leq e\).

  1. Determine the numbers \(x\) at which \(f\) has its absolute maximum and absolute minimum.
  2. For what numbers \(x\) is the graph concave up?
  3. Graph \(f\).

Question

Probability The function \(f(x)=\dfrac{1}{\sqrt{2\pi }} e^{-x^{2}/2}\), encountered in probability theory, is called the standard normal density function. Determine where this function is increasing and decreasing, find all local maxima and local minima, find all inflection points, and determine the intervals where \(f\) is concave up and concave down. Then graph the function.

In Problems 61–64, graph each function. Use L’Hôpital’s Rule to find any asymptotes.

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\(f(x)=\dfrac{\sin (3x)}{x\sqrt{4-x^{2}}}\)

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\(f(x)=x^{\sqrt{x}}\)

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\(f(x)=~x^{1/x}\)

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\(y=\dfrac{1}{x}\tan x\quad -\dfrac{\pi }{2}<x<\dfrac{\pi}{2}\)