Question

Find the sum of first 22 terms of AP 8,3,-2.​

Answer 1

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Step-by-step explanation:

We have to find the sum of first 22 terms.

Sum = n/2 [2a+[n-1]d]

here n = 22 , a = 8 , d = 3 - 8 = -5

Putting there values in formula,

Sum = n/2 [ 2a+[n-1] d ]

        = 22/2 [ 2*8+[22-1] [ -5 ] ]

        = 11 [ 16+[21] [ -5 ] ]

        = 11 [ 16-105 ]

        = 11 [ - 89 ]

        = -979

so,the sum of first 22 terms of AP 8,3,-2 is -979. [ ANSWER ]

Answer 2

Answer:

$\sf Here,~ a= 8,~d= 3-8=- 5,~ n= 22 \\ \\ \bf S_n = \dfrac {n}{2} [2a+(n-1) d] \\ \\ \bf s_{22} = \dfrac {22}{2} [16 +(22-1)(-5)] \\ \\ \bf s_{22} = 11 (16-105) \\ \\ \bf s_{22} =11 (-89) \\ \\ \bf s_{22} = -979$