Answer:

Step-by-step explanation:
we know that
The absolute value function has two solutions
Observing the graph
the solutions are
and 
First solution (case positive)
assume the symbol of the first solution and then compare the results




Second solution (case negative)

Multiply by -1 both sides

substitute the value of b and compare the results


-------> is correct
Answer:
The sample would double in 9 hours
Step-by-step explanation
The number of hours it will take for the sample to double can be found using the 72 rule.
The 72 rule is such that a growth rate would double itself by it is used in dividing the number 72 as shown below:
number of hours =72/8=9 hours
The number of hours it would take the sample to double is 9 hours as computed above.
They aren't the same number
The formula for the area of a circle is PI x radius^2.
To find the area of the sector, you would multiply the area by the ratio of the the sector angle over 360.
The formula would become PI x r^2 x 30/360.
The 2nd choice is correct.