Question

Find the answer fast plz

Answer 1

n--→n-1
Sn-1=(n-1)²[n-1+1]
Sn-1=n²+1-2n(n)
Sn-1=n³+n-2n²
tñ=(Sn-1)-(Sn)
tñ=-1
on putting n=-1
T1=-1
therefore, the first term of the series is -1