No.15, Prove by PMI
Kindly refer the similar link for your query.
https://www.meritnation.com/cbse/class11-science/textbook-solutions/math/rd-sharma-xi-(2015)/mathematical-induction/page12.28-exercise-12.2-qno18/1265_6789_70840
Regards
https://www.meritnation.com/cbse/class11-science/textbook-solutions/math/rd-sharma-xi-(2015)/mathematical-induction/page12.28-exercise-12.2-qno18/1265_6789_70840
Regards