Proceed as in this example to rewrite each power series as a power series whose general term involves $x^k.$

${\displaystyle \underset{n=2}{\overset{}{}}}n(n-1)c_n{x}^{n-2}={\displaystyle \underset{k=1}{\overset{}{}}}()x^k$

$6{\displaystyle \underset{n=1}{\overset{}{}}}n{c}_n{x}^n={\displaystyle \underset{k=1}{\overset{}{}}}()x^k$

${\displaystyle \underset{n=0}{\overset{}{}}}{c}_n{x}^n=$

Rewrite the given expression using a single power series whose general term involves $x^k.$