1.

2. a) 35 b) 4.2

3.

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)=1500.2^{4}=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)