I am stuck on this proof, but this is what i have done so far.

When n=1 it is ture as (1+a)^1>= 1+a

we can know assume P(k) is true:

(1+a)^k>= 1+Ka

so for P(K+1)= (1+a)^k+1>= (1+Ka)(1+K)

>= (1+k+ka+k^2a)

this looks wrong to me and i cannot figure it out on how to finish this proof can so one please help me.

Thanks