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2. a) 35 b) 4.2


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4. The solutions are x=2 and x=-1

5.

6.a) n(t)=1500 .2^t/30 (t in minutes)
b) The number of bacterias after two hours is
n(120)=1500.2⁴=24000
c) Solving the equation n(t)=4000 one gets t=30 ln(8/3)/ln(2)
(One can use logarithm in other basis. The answer can “look” different)