Question

Suppose that the cost of using solar energy to heat a home involves an initial cost of $10,000 with an average yearly cost of $200 for every year after the first. Suppose also that heating with oil involves an initial cost of $4000 with an average yearly cost of $800 for every year after the first. Use the graph below as a model to graph this information on a separate sheet of paper and answer the questions given.
What are the coordinates of the point where the lines intersect?

Answer 1

Let s(x) represent usage of solar energy:
Let o(x) represent usage of oil:
s(x)=o(x) where they intersect
10000+200x=4000+800x
6000=600x
x=10, find y:
4000+800(10)=10000+200(10)=12000
(10, 12000)

Answer 2

is it (12,10)

Answer 3

(10,12000)

Answer 4

it does't have a answer choice with 1200

Answer 5

what are the choices?

Answer 6

a) (10,11)
b) (11,12)
c) (12,11)
d) (12,10)

Answer 7

Are the y-units represented in thousands of dollars?

Answer 8

no

Answer 9

OK, i slightly misread the problem. Every year AFTER the first it cost 200x or 800x.
So:
10000+200(x-1)=4000+800(x-1)
6000=600(x-1)
6000=600x-600
6600=600x
x=11

Answer 10

I still get 12000 for the y-value. Out of those choices, I'd assume they are representing the y-axis in thousands; I'd go with option B.