Question

t₁₉ = ? for the given A.P., 9, 4, −1, −6 ........

Activity :- Here a = 9, d = `square`

t_n = a + (n − 1)d

t₁₉ = 9 + (19 − 1) `square`

= 9 + `square`

= `square`

Answer 1

Here a = 9, d = 4 - 9 = − 5

t_n = a + (n − 1)d

t₁₉ = 9 + (19 − 1) − 5

= 9 + 18(-5)

= 9 + − 90

= − 81