Question

29. Find the sum : 34 + 32 + 30 + ... + 10​

Answer 1

a = 34

d = 32 – 34 = –2

Añ = 10

Or, a + (n – 1) d = 10

Or 34 + (n – 1) (–2) = 10

Or –2 (n – 1) = –24

Or, n – 1 = 12

n = 13

S13 = 13/2 [2(34) + 12(–2)]

= 13/2 × 2(34–12)

= 13 × 22 = 286.

Answer 2

ANSWERS :

a = 34

d = 32 - 34 = - 2

a^ n = 10

or a + (n - 1 ) d = 10

or 34 + (n - 1 ) ( - 2) = 10

or - 2 (n - 1) = - 24

or n - 1 = 12

= n = 13

.°. S ^ 13 = 13 / 2 [ 2(34) + 12 ( - 2 )]

= 13/ 2 × 2 [ 34 - 12 ]

13 × 22 = 286

That's all

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