Question

Suppose a one year subscription to a magazine cost $12.99 and a three-year subscription cost $25.98 the cost and length of the subscription are related write an equation to a model the cost of a subscription for any period of time

Answer 1

y = $38.97

y = 6.495(5) + 6.495

Explanation:

So for this problem, since it states the cost and length of the subscription are related, you can use the two subscription costs as data (or coordinate) points.

1 year = 12.99, 3 year = 25.98; so (1,12.99), (3, 25.98) use these points to calculate the average rate of change (or the slope (m)).

(y - y1)/(x - x1) = m so, (25.98-12.99)/(3 - 1) = 6.495, this is the slope, m

y = 6.495(x) + b now just pick one of the points and put in the x and y values to solve for b

12.99 = 6.495(1) + b solve for b and you discover it also = 6.495 = b

so y = 6.495(x) + 6.495 is the equation of the line, to answer their question, just pop in x=5 for the 5 years subscription cost

y = 6.495(5) + 6.495

y = $38.97