Question

I need help in algebra 1. I have 4 questions, I already answered 3 of them, but I need help with the other

Andrew measures the amount of a very unstable substance to be 100 moles. The half-life of this substance is 3 days (after 3 days, half is gone).

1. Write an exponential function that models this situation where y is the amount of substance and x is time in days.
I think it's: y=100^.(1/2)^t/3

2. Use your equation from problem 1 to complete the chart:

Days Amount
-3 (3 days prior) 200
0 100
3 50
6 25
9 12.5
12 6.25

Did I fill in the chart correctly?

3. Use your data from problem 2 to graph your equation from problem 1

I'm not sure how to graph it :/

4. Calculate the expected amount of substance if Andrew had taken his measurements 9 days earlier. Show your calculations and consider the tend of your graph for problem 3
My answer:
x=-9
y=100^.(1/2)^-3
y=100^.(1/2)^-9/3
y=100^.(1/2)^-3=100^.8=800 moles

All help appreciated! Thanks!

Answer 1

1. yes y = 100 (1/2)^(t/3)
2. looks good, divide by 2 every three days
3. I can not very well show you a graph
maybe google
graph exponential
or graph A * B^-(kt)

4. 100 /(1/2)^3 = 100/(1/8) = 800
so yes but do not understand how you did it

Answer 2

Okay thank you so much Damon! :D

Answer 3

apparently her notation is ^. for * meaning multiply.

Trés strange.