SOLUTION: So I need help with these exponential function problems. I have solved for the most part using Logarithms, but I still do not understand how to graph them, I need to show full solu

Question 1155437: So I need help with these exponential function problems. I have solved for the most part using Logarithms, but I still do not understand how to graph them, I need to show full solutions so I thought if i graphed them The teacher would understand
A bicycle loses its value each month after it is purchased. It’s value as a function of time, in months, is modelled by V(m)=2200(0.98)^m. In which month after it is purchased does the bicycles worth fall below $1,500?
A 150 g sample of protactinium-233 has a half-life of 27 days. How long will it take for this sample to decay to 100 g?
Answer by greenestamps(13216) (Show Source): You can put this solution on YOUR website!

It's not clear what help you are asking for....

The easiest way to solve problems like these is with a graphing calculator.

For the first problem, graph the functions and and find their point of intersection.

Algebraically,

= 18.96 to 2 decimal places

ANSWER: It will take 19 months for the value to drop below $1500.

For the second problem about half lives, the formula is

where x is the number of half-lives. For your problem,

Again the easiest solution is with a graphing calculator.

Algebraically,

= 0.585 to 3 decimal places.

ANSWER: It will take about 0.585 half lives, or 0.585*27 = 15.8 days, for the amount to drop to 100g.

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