Question

rn Find the sum to n terms of the series : 5+11+19+29+41+…

Answer 1

5+11+19+29+41+......

(2^2+1)+(3^2+2)+(4^2+3)+(5^2+4)+.....{(n+1)2+n}

(r+1)^2+r=r^2+3r+1

now use concept of sigma

sigma.r^2+ 3sigma.r+sigma.1

n (n+1)(2n+1)/6 + 3n (n+1)/2 +1

above is sum of n term given series

Answer 2

Please see the attachment: