Question

Sum the series n.1+(1-1).2 + (n - 2).3 + ......+1.n​

Answer 1

Answer:

the r th term will be r(n-r+1)

it is summation of r(n-r+1) where r varies from 1 to n;

SUM ( (n+1)r - r^2 ) = (n+1)(n)(n+1)/2 - (n)(n+1)(2n+1)/6

Thanks and Regards,

Answer 2

Answer:

Please find the attachment