Question

Find the 27^th term of the following A.P.
9, 4, –1, –6, –11,...

Answer 1

The given sequence is 9, 4, –1, –6, –11,...
Here,
First term (a) = 9 
Common difference (d) = a₂ – a₁ = 4 – (9) = –5
Now,

\[a_{27} = a + \left( n - 1 \right)d\]
\[ = 9 + \left( 27 - 1 \right)\left( - 5 \right)\]
\[ = 9 + \left( 26 \right)\left( - 5 \right)\]
\[ = - 121\]

Hence, the 27^th term of the progression is –121.