Question

Find the 12^th term from the last term of the A.P – 2, – 4, – 6, … – 100

Answer 1

n = `("l" - "a")/"d" + 1`

= `(-100 - (- 2))/(-2) + 1`

= `(- 100 + 2)/(-2) + 1`

= `(-98)/(-2) + 1`

n = 49 + 1

= 50

12^th term from the last = 39^th term from the beginning

∴ t₃₉ = a + 38d

= – 2 + 38(– 2)

= – 2 – 76

= – 78