Use mathematical induction to prove the statement is true for all positive integers n.1 + 3 + 32 + . . . + 3n - 1 =

Question

What will be an ideal response?

Answer 1

Answers may vary. Possible answer:
First we show that the statement is true when n = 1.
 For n = 1, we get 1 = 
 Since  =  = 1 , P₁ is true and the first condition for the principle of induction is satisfied.
Next, we assume the statement holds for some unspecified natural number k. That is,
P_k:  is assumed true.
On the basis of the assumption that P_k is true, we need to show that P_k+1 is true. 
P_k+1: 
So we assume that  is true and add the next term,  to both sides of the equation.  






 The last equation says that P_k+1 is true if P_k is assumed to be true. Therefore, by the principle of mathematical induction, the statement 1 + 3 + 3² + ... + 3^{n - 1} =   is true for all natural numbers n.