∑(r^2+1)(r!), r ∈ (1, 20) is equal to

Question

\(\displaystyle\sum_{r=1}^{20} \) (r² + 1) (r!) is equal to :

(A) 22! – 21! 

(B) 22! – 2 (21!) 

(C) 21! – 2 (20!) 

(D) 21! – 20!

Answer 1

(B) 22! – 2 (21!)