Question

Find the 19^th term of an A.P. – 11, – 15, – 19, ...

Answer 1

A.P = – 11, – 15, – 19, ...

a = – 11

d = t₂ – t₁ = – 15 – (– 11)

= – 15 + 11

= – 4

n = 19

∴ t_n = a + (n – 1)d

t₁₉ = – 11 + (19 – 1)(– 4)

= – 11 + 18 × – 4

= – 11 – 72

= – 83