Okay, so I have two practice questions that I am really struggling with.

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Hi tannawirsch,

1. An unknown artist painting was worth $85 in 1978. As the artist grew in popularity, the value of this painting grew in value at the rate of 9% per year.
A) Write an equation to represent the value (y) in dollars of the painting as a function of the number of years (c) since 1978?

y=85(1+0.09) ^c

Now you think about why this is so. What will it be worth after 1 year, after 2 years, what is the pattern.

2. Caffeine found in pop, coffee, and tea; travels in your bloodstream after you consume it. After you drink a beverage that contains caffeine, 13% of the caffeine in your bloodstream is removed every hour. *Initially 100% is present, so A=100.
A) Write an equation to represent the percent of the caffeine (y) that remains in your bloodstream (x) hours after you drink it?

y=(1-0.13) ^x

Thank you SO much for your help! Although I've got one question about this.

I tried to put it into a graph and it doesn't work. I need an equation that is able to be used in a graph.

Sorry, I should have mentioned that earlier.

tannawirsch:

Thank you SO much for your help! Although I've got one question about this.

I tried to put it into a graph and it doesn't work. I need an equation that is able to be used in a graph.

Sorry, I should have mentioned that earlier.

Hi again tannawirsch,

Why can't you graph it?

They are both in the positive quadrant only.
The first one has c on the horzontal axis, the second on has x on th horizontal axes.
They both have y on the vertical axis.

For the first one start c=1,c=2, etc and calculate the y value that goes with it and then graph.

For the second one the y axis has to go from 0 to 100%
Work out some points starting with x=0,x=1, etc and calculate the y values that go with them and then graph it.

I have tried over and over again to try and graph it but in the end it doesn't work.

Part of the question states to create a graph using the values from (c) from 0 to 12, but as I replace (c) with numbers from 0 to 12, I end up with straight horizontal line across the graph.

Ok

Question1 - This is the graph.

140131 exp graph.JPG

Okay, thank you much.