Question

If the 5th term of an arithmetic sequence is 11 and the 16th term is -77, find the 20th term.

Answer 1

Answer:

5th term =11,

16th term =-77

let first term be a

CD be d

=>5th term is a+4d=11----------->[1]

16th term is a+15d= -77------>[2]

[1]-[2]=> -11d=88=>d= -8

:.a=11+32=43

=>20th term is a+19d=43-152

= -109