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1.8.8 Integration by substitution (A-level only)

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Question 50

The rate of growth of a specific bacteria population in a petri dish, G(t)G(t)G(t) in thousands of bacteria per hour, is modeled by the function

G(t)=122+2t+4 G(t) = \frac{12}{2 + \sqrt{2t + 4}} G(t)=2+2t+4​12​

for 0≤t≤160 \le t \le 160≤t≤16, where t t\,t is the time in hours since the start of the experiment. Using the substitution u=2+2t+4u = 2 + \sqrt{2t + 4}u=2+2t+4​, find the exact total increase in the population over the 16-hour period by calculating the value of

∫016122+2t+4 dt \int_{0}^{16} \frac{12}{2 + \sqrt{2t + 4}} \, dt ∫016​2+2t+4​12​dt

Give your answer in the form a+bln⁡ca + b \ln ca+blnc, where a,b, a, b,\,a,b, and c c\,c are integers.

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1.8.8 Integration by substitution (A-level only) Questions

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