(Q13).Find the sum of the following APs:

(ii) -37, -33, -29,…, to 12 terms.

Given A.P: -37, -33, -29,…, to 12 terms.

a = -; d = a2 – a1 = (-) – (-) = - + = ; n =

Sn =
n
2
 [2a + (n-1)d]
∴ S12 =
2
 [2 × (-) + (-1)]

= [- + × ]

= [- + ]

= × (-)

= -