Solve. Assume the exercise describes a linear relationship. When writing a linear equation, write the equation in
slope-intercept form.
-When making a telephone call using a calling card, a call lasting 3 minutes costs $1.00. A call lasting 11 minutes costs $2.60. Let y be the cost of making a call lasting x minutes using a calling card. Write a linear equation that
Models the cost of making a call lasting x minutes.
A)y = 0.2x - 8.4
B)y = 5x - 14
C)y = -0.2x + 1.6
D)y = 0.2x + 0.4

Question

Quizplus · Accepted Answer

To find the slope (m) of the line, we use the formula $m = \frac{y_2 - y_1}{x_2 - x_1}$, where $(x_1, y_1)$ and $(x_2, y_2)$ are points on the line. Here, the points are (3, 1) and (11, 2.6), so $m = \frac{2.6 - 1}{11 - 3} = \frac{1.6}{8} = 0.2$. To find the y-intercept (b), we use one of the points and the slope in the equation $y = mx + b$. Using (3, 1), we get $1 = 0.2(3) + b$, leading to $b = 1 - 0.6 = 0.4$. Thus, the equation is $y = 0.2x + 0.4$.

Solve Assume the Exercise Describes a Linear Relationship