Question

The sum of the firstnith term of series

is given by Sn = n2+ 5 n-6. Find the
general term (tn) and (+20)​

Answer 1

Tn = 2n+4

T20 = 44

Explanation:

Given Sn = n²+ 5 n-6

Tn = Sn - Sn-1

Sn-1 = (n-1)² + 5(n-1) - 6

Tn = n²+ 5n-6 - ((n-1)² + 5(n-1) - 6))

Tn = n²+ 5n-6-(n²-2n+1+5n-5-6)

Tn = n²+ 5n-6-n²+2n-1-5n+5+6

Tn = 2n-7+11

Tn = 2n+4

Get the general term is 2n+4

To get the 20th term;

T20 = 2(20) + 4

T20 = 40+4

T20 = 44

Hence the 20th term of the sequence is 44