Let

be the statement that

Check to see that

holds for

:

Now suppose that

is true, and use that assumption to show that

must also be true. When

, you have




and so

is also true, thus proving the statement is true for all

.
Part A: After 9 days the radius of algae was approximately 12.81 mm. The reasonable domain to point is (0,9).
Part B: The 9 on the y-intercept represents the amount of algae the experiment started with.
Part C: (12.81-10.12)/7=0.38