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1 Pure Mathematics

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Question 346

A biologist is monitoring the population of a specialized algae culture, PPP (in thousands), in a controlled environment. At time ttt hours (t>0t > 0t>0), the rate of change of the population is modeled by the derivative:

P′(t)=2t2+at+b3t P'(t) = \frac{2t^2 + at + b}{3\sqrt{t}} P′(t)=3t​2t2+at+b​

where aaa and bbb are constants. It is observed that at time t=4t = 4t=4, the population is exactly 10,000 algae (P=10P = 10P=10) and the population is growing at a rate of 5,000 algae per hour (P′=5P' = 5P′=5).

a.

Show that 4a+b=−24a + b = -24a+b=−2.

[3]
b.

Given also that a+b=7a + b = 7a+b=7,

Determine, in simplest form, an expression for P(t)P(t)P(t).

[5]
c.

A researcher adjusts the experiment such that the new population model is given by G(t)=P(t−3)G(t) = P(t - 3)G(t)=P(t−3). Given that the observation at t=4t = 4t=4 in the original model is recorded as point JJJ,

State the coordinates of the corresponding point KKK on the graph of G(t)G(t)G(t).

[1]
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1 Pure Mathematics Questions

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