Question

(9) Find the sum of the first 22 terms of the AP : 8, 3, -2,
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Answer 1

Answer:

-979

Step-by-step explanation:

S22 = (22/2)[16+21*(-5)]

= 11*[16-105]

= -11*89

= -979

Answer 2

AP : 8, 3, -2 ..

Here ..

• First term (a) = 8

• Common difference (d) = a2 - a1

=> 3 - 8 = - 5

• Number of terms (n) = 22

_____________ [ GIVEN ]

• We have to find the sum of first 22 terms.

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→ $S_{n}$ = $\dfrac{n}{2}$ [2a + (n - 1)d]

Put the known values in above formula

→ $S_{22}$ = $\dfrac{22}{2}$ [2(8) + (22 - 1)(-5)]

→ $S_{22}$ = 11[16 + 21(-5)]

→ $S_{22}$ = 11(16 - 105)

→ $S_{22}$ = 11 (-89)

→ $S_{22}$ = - 979

____________________________

- 979 is the sum of first 22 terms.

_______ [ ANSWER ]

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