Since 1990, when the average monthly price for basic cable TV programming in one country was $15.81, the cost has risen by about $1.12 a year. Write an equation in slope-intercept form to predict cable TV costs in the future. Use t to represent time in years after 1990 and C to represent the average basic monthly cost.
A) $C = - 15.81 t + 1.12$
B) $C = 1.12 t + 15.81$
C) $C = 15.81 t - 1.12$
D) $C = - 1.12 t + 15.81$
E) $C = 1.12 t - 15.81$

Question

Quizplus · Accepted Answer

The slope of the equation is the rate at which the cost is increasing. We are given that the cost has risen by $1.12 a year, so the slope is 1.12. The y-intercept of the equation is the cost when t is 0 (i.e. in 1990). We are told that the average monthly price in 1990 was $15.81, so the y-intercept is 15.81. Therefore, the equation in slope-intercept form is:
C = 1.12t + 15.81

Since 1990, When the Average Monthly Price for Basic Cable C=−15.81t+1.12C = - 15.81 t + 1.12C=−15.81t+1.12

Since 1990, When the Average Monthly Price for Basic Cable $C = - 15.81 t + 1.12$