Answer: 
Step-by-step explanation:
We know that the general form of the exponential decay formula is
, where y is final amount remaining after t time, A is the original amount and r is the rate of decay
Now, the ratio of strontium-90 remaining, p , as a function of years, t , since the nuclear accident. 
Hence, the ratio of remaining since the nuclear accident is 
Answer: Explicit Rule: a_n=30,000 • 2^n-1
Recursive Rule: a_n = 2a_n-1; a_1 = 30,000
Step-by-step explanation: the explicit rule for a geometric sequence is a_n = a_1 • r^n-1 and the recursive rule is a_n= r • a_n -1.
a_1 is the first term of the sequence, which is this case is 30,000. R is the common ration, which is 2 since it doubles each time. Substitute those numbers into the formulas and that’s what you’ll get. Hope this helps. God bless you!!!
Answer:
z^ {8/5}
Step-by-step explanation:

I hope this helps, i got it from a cheat sheet online
Answer:
The probe's final position is -143m
Step-by-step explanation:
Note that the words 'lowered' and 'below' mean subtract; while the word 'raised' means add. Thus, interpreting the statement to mathematical expression is done below.


Therefore, the probe's final position is -143m. Hence, the sensor is 143m below the sea level.