Practice Problems: Problems | Saylor Academy

Problems

1. In Fig. 9 , find the location of the number(s) "c" which Rolle's Theorem promises (guarantees).

Fig. 9

For problem 3, verify that the hypotheses of Rolle's Theorem are satisfied for each of the functions on the given intervals, and find the value of the number(s) " $c$ " which Rolle's Theorem promises exists.

3. (a) $\mathrm{f}(\mathrm{x})=\sin (\mathrm{x})$ on $[0, \pi]$
(b) $f(x)=\sin (x)$ on $[\pi, 5 \pi]$

5. Suppose you toss a ball straight up and catch it when it comes down. If $\mathrm{h}(\mathrm{t})$ is the height of the ball at time $t$ , then what does Rolle's Theorem say about the velocity of the ball? Why is it easier to catch a ball which someone on the ground tosses up to you on a balcony, than for you to be on the ground and catch a ball which someone on a balcony tosses down to you?

7. If $\mathrm{f}(\mathrm{x})=|\mathrm{x}|$ , then $\mathrm{f}(-1)=1$ and $\mathrm{f}(1)=1$ but $\mathrm{f}^{\prime}(\mathrm{x})$ is never equal to $0$ . Why doesn't this function violate Rolle's Theorem?

9. If I take off in an airplane, fly around for awhile and land at the same place I took off from, then my starting and stopping heights are the same but the airplane is always moving. Doesn't this violate Rolle's theorem which says there is an instant when my velocity is $0$ ?

11. Use the corollary in problem 10 to justify the conclusion that the only root of $f(x)=x^{3}+5 x-18$ is $2$ . (Suggestion: What could you conclude about $\mathrm{f}'$ if $\mathrm{f}$ had another root?)

In problems 13-15, verify that the hypotheses of the Mean Value Theorem are satisfied for each of the functions on the given intervals, and find the value of a number(s) " $c$ " which Mean Value Theorem guarantees.

13. (a) $f(x)=x^{2}$ on $[0,2]$
(b) $f(x)=x^{2}-5 x+8$ on $[1,5]$

15. (a) $f(x)=5-\sqrt{x}$ on $[1,9]$
(b) $\mathrm{f}(\mathrm{x})=2 \mathrm{x}+1$ on $[1,7]$

17. If $f(x)=|x|$ , then $f(-1)=1$ and $f(3)=3$ but $f^{\prime}(x)$ is never equal to $\frac{f(3)-f(-1)}{3-(-1)}=\frac{1}{2}$ . Why doesn't this function violate the Mean Value Theorem?

In problem 19, you are a traffic court judge. In each case, a speeding ticket has been given and you need to decide if the ticket is appropriate.

19. The driver in the next case heard the toll taker and says, "Your Honor, my average velocity on that portion of the toll road was only 17 miles per hour, so I could not have been speeding. I don't deserve a ticket".

21. Find a function $f$ so that $f^{\prime}(x)=3 x^{2}+2 x+5$ and $f(1)=10$ .

23. Find values for $\mathrm{A}$ and $\mathrm{B}$ so that the graph of the parabola $\mathrm{f}(\mathrm{x})=\mathrm{Ax}^{2}+\mathrm{B}$ is
(a) tangent to the line $\mathrm{y}=4 \mathrm{x}+5$ at the point $(1,9)$
(b) tangent to the line $\mathrm{y}=7-2 \mathrm{x}$ at the point $(2,3)$
(c) tangent to the parabola $\mathrm{y}=\mathrm{x}^{2}+3 \mathrm{x}-2$ at the point $(0,2)$

25. Sketch the graphs of several members of the "family" of functions whose derivatives always equal $3 \mathrm{x}^{2}$ . Give a formula which defines every function in this family.

27. Assume that a rocket is fired from the ground and has the upward velocity shown in Fig. 11. Estimate the height of the rocket when $t=1, 2$ , and $5$ seconds.