The sound level $9.75 \mathrm{~m}$ from a loudspeaker, placed in the open, is $115 \mathrm{~dB}$. What is the acoustic power output (W) of the speaker, assuming it radiates equally in all directions?

Sketch the graph of the function "by hand" after making a sign diagram for the derivative and finding all open intervals of increase and decrease.

$$f(x)=-x^4+4 x^3-4 x^2+1$$

In Exercises, find the critical numbers of $f$ (if any), find the open intervals on which the algebraic function is increasing or decreasing, and locate all relative extrema.

$f(x)=\frac{x^5-5 x}{5}$

In Exercises, find the critical numbers of $f$ (if any), find the open intervals on which the algebraic function is increasing or decreasing, and locate all relative extrema.

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

The Norwich cranberry bog can be filled in $9 \mathrm{~hr}$ and drained in $11 \mathrm{~hr}$. How long will it take to fill the bog if the drainage gate is left open?

Two equal-size rooms communicate through an open doorway. However, the average temperatures in the two rooms are main- tained at different values. In which room is there more air?

If the humidity in a sealed room of volume $420 \mathrm{~m}^3$ at $20^{\circ} \mathrm{C}$ is $65 \%$, what mass of water can still evaporate from an open pan?

State whether the following sentence is true or false. If false, replace the underlined term to make a true sentence.

A $\underline{\text{point}}$ defines the boundary of an open half-plane.

Squares with sides of length x are cut out of each corner of a square piece of cardboard with sides of length $\ell$. Find the volume of the largest open box that can be formed in this way.

For each of the following sentences, write the past or past participle of the verb given in parentheses.

Please open the note and read what I have $\underline{\hspace{3cm}}$. (write)

Why does the priority system described in this chapter require that it be open and published? Does the process encourage bottom-up initiation of projects? Does it discourage some projects? Why?

Why is your vision so blurry when you open your eyes while swimming under water? How does a face mask enable clear vision?

In Exercises, find the open intervals on which the function is increasing or decreasing, and locate all relative extrema. Use a graphing utility to confirm your results.

$f(x)=(x-1)^{1 / 3}$

In Exercises, find the critical numbers of $f$ (if any), find the open intervals on which the algebraic function is increasing or decreasing, and locate all relative extrema.

$$f(x)=-2 x^2+4 x+3$$