Let n with n 2 Prove by induction that 3n n 2n Hint If n 2 t
Let n with n 2. Prove by induction that 3n n 2n. Hint: If n 2, then 3n 2n + 2 (why?).
Solution
n is any natural number greater than or equal to 2.
n can be 2,3,4,5......
To prove that 3n>=2n+2
Let n =2 then 3n = 6 >=2(2)+2
Thus true for n =2
---------------------------------
Assume true for n = k
i.e. 3k >= 2k+2
To prove that true for n = k+1
To prove that 3(k+1) >=2(k+1)+2
Left side = 3k+3 >= 2k+2+3 by the assumption for n = k
i.e. Left side >= 2k+5 = 2k+4+1
=2(k+1) +3
>= 2(k+1)+2
Thus if true for n=k true for n = k+1 also
Holds good for all natural numbers

