A population of beetles are growing according to a linear growth model. The initial population (week 0) is P0=5\displaystyle {P}_{{0}}={5}, and the population after 6 weeks is P6=47\displaystyle {P}_{{6}}={47}.

Find an explicit formula for the beetle population after n\displaystyle {n} weeks.

Pn\displaystyle {P}_{{n}} =  

After how many weeks will the beetle population reach 145?

  weeks