True, if a points works in both equations of a linear system, then that point is the solution.
The answer is D.
You cannot factorise it as there are two different terms being squared with the middle term containing both. Also, if you expand any of the brackets in the questions you will not get the original equation so non of them are right so it has to be D. :)
Answer:
9,942 bacteria were there at 10 hours.
Step-by-step explanation:
Equation for population decay:
The equation for population decay, after t hours, is given by:

In which P(0) is the initial population and r is the decay rate, as a decimal.
Researchers recorded that a certain bacteria population declined from 200,000 to 900 in 18 hours.
This means that
and that when
. So we use this to find r.



![\sqrt[18]{(1-r)^{18}} = \sqrt[18]{\frac{900}{200000}}](https://tex.z-dn.net/?f=%5Csqrt%5B18%5D%7B%281-r%29%5E%7B18%7D%7D%20%3D%20%5Csqrt%5B18%5D%7B%5Cfrac%7B900%7D%7B200000%7D%7D)


So


At this rate of decay, how many bacteria was there at 10 hours?
This is P(10). So

Rounding to the nearest whole number:
9,942 bacteria were there at 10 hours.