Question

find the sum of first 22 terms of the AP 8,3,-...

Answer 1

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Given A.P : 8,3,......

The sum of the first n terms of an AP is founded by using the formula Sn :

• Sn = n/2 { 2a + ( n - 1 ) d }

Where , Sn = sum of the n term.

               d =  ( common difference ) a₂ - a₁

               a = 1st term

               

Your answer starts from here :

• 8,3,......
• Here, a = 8 , d = 3-8 = -5 and n = 22

We know that :

Sn = n/2 { 2a + ( n - 1 ) d }

Therefore,

S₂₂  =  22/2 { 16 + 21 ( - 5 ) }

S₂₂  =  11 ( 16 - 105 )

S₂₂  =  11 ( - 89 )

S₂₂  =   - 979

Hence, the sum of first 22 terms of the AP is - 979.

Answer 2

Answer:

Your answer starts from here :

8,3,......

Here, a = 8 , d = 3-8 = -5 and n = 22

We know that :

Sn = n/2 { 2a + ( n - 1 ) d }

Therefore,

S₂₂ = 22/2 { 16 + 21 ( - 5 ) }

S₂₂ = 11 ( 16 - 105 )

S₂₂ = 11 ( - 89 )

S₂₂ = - 979

Hence, the sum of first 22 terms of the AP is - 979.