Question

we have an =4 d =2 sn = -14 find n and a

Answer 1

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

sn = n /2 ( a + 2 ( n - 1 )

-14 x 2 = an + 2n ( n - 1 )

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an = 4

⭕⭕⭕⭕⭕⭕⭕⭕⭕⭕⭕⭕⭕⭕

-28 = 4 + 2n ( n - 1 )

-28 - 4 = 2n ( n - 1 )

-32 = 2n^2 - 2n

2n^ 2 - 2n + 32 = 0

NOW BY USING FACTOR METHOD ....

WE CAN SOLVE IT ....

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