Question

Find the sum to 20 terms of the series 6 + 30 + 70 +126 + ... ... ... ...​

Answer 1

Answer:

Sn= n/2[2a+(n-1)d]

S20=20/2 [2×6+(20-1)24]

=10 [12+(19)24]

=10 [12+456]

=10×468

=4680