Answer:
See explanation
Step-by-step explanation:
1 step:
n=1, then

So, for j=1 this statement is true
2 step:
Assume that for n=k the following statement is true

3 step:
Check for n=k+1 whether the statement

is true.
Start with the left side:

According to the 2nd step,

Substitute it into the 

So, you have proved the initial statement