∑∞k=10 (([k+2)(k+1)x^(k+1)])/k+3)=∑∞k=1 ...............
Hint: Let u = k-9. Then write all as an expression as u. Then let u=k.
Show ur steps if need be and we can take it from there.
Thanks the solution is ((k+11)(k+10)x^(k+10))/(k+12)