Communications The cost of using a telephone calling card is $\$ 1.05$ for the first minute and $\$ 0.38$ for each additional minute or portion of a minute.
Graph the appropriate model. Determine the cost of a call lasting $18$ minutes and $45$ seconds.

In Exercise, solve the quadratic equation by factoring.

$-x^2+8 x=12$

Communications The cost of using a telephone calling card is $\$ 1.05$ for the first minute and $\$ 0.38$ for each additional minute or portion of a minute.
A customer needs a model for the cost $C$ of using a calling card for a call lasting $t$ minutes. Which of the following is the appropriate model? Explain.

$$\begin{aligned} &C_1(t)=1.05+0.38 \llbracket t-1 \rrbracket \\ &C_2(t)=1.05-0.38 \llbracket-(t-1) \rrbracket \end{aligned}$$

An experiment in a physics lab requires a student to measure the compressed length $x$ (in centimeters) of a spring when a force of $F$ pounds is applied. The data is shown in the table.

Sketch a scatter plot of the data.

Find the slope-intercept form of the equation of the line that passes through the given point and has the indicated slope m. Sketch the line. $\left(-\frac{1}{2}, \frac{3}{2}\right), \quad m=0$

In this exercise, find the standard form of the equation of the specified circle.

Endpoints of a diameter: $(-4,-1),(4,1)$

determine whether the function has an inverse function. If it does, then find the inverse function. f(x) = { -x, x ≤ 0 . x^2-3x, x > 0

Prove that the product of two odd functions is an even function, and that the product of two even functions is an even function.

determine whether the function is even, odd, or neither. Then describe the symmetry. f(x) = x√1-2^2

use a graphing utility to graph the function and visually determine the intervals on which the function is increasing, decreasing, or constant. f(x) = (x^2 - 4)^2

find the domain of the function. h(x) = 10 / x^2-2x

Find the distance between a and b. a=9.34, b=-5.65.

Fuel Use The amount of fuel $F$ (in billions of gallons) used by trucks from $1980$ through $1999$ can be approximated by the function

$$F=f(t)=20.5+0.035 t^2$$

where $t=0$ represents $1980.$
Use the model from the previous part to predict the amount of fuel used by trucks in $2005$. Does your answer seem reasonable? Explain.

An oceanographer took readings of the water temperature $C$ (in degrees Celsius) at depth $d$ (in meters). The data collected is shown in the table.

Use the model to approximate the depth at which the water temperature is $3^{\circ} \mathrm{C}$.