Ap afCl

1.	Ap afCl
Answer» an = a+(n-1)d = a+(n-1)2 = a+2n -2 = 4 => a+2n = 6=> a = 6-2n sn = n/2(a+an) => -142 = n( a+4)=> an + 4n = -28 => n(6-2n+4) = -28=> -2n²+10n+28. = 0=> n²-5n-14 = 0=> n²-7n+2n-14 = 0=> n(n-7) +2(n-7) = 0=> (n+2)(n-7) = 0=> n = 7 , -2 but n can't be -ve , so n = 7 and a = 6-2n = 6-27 = -8

Answer»

an = a+(n-1)d = a+(n-1)2 = a+2n -2 = 4 => a+2n = 6=> a = 6-2n

sn = n/2(a+an) => -14*2 = n( a+4)=> an + 4n = -28 => n(6-2n+4) = -28=> -2n²+10n+28. = 0=> n²-5n-14 = 0=> n²-7n+2n-14 = 0=> n(n-7) +2(n-7) = 0=> (n+2)(n-7) = 0=> n = 7 , -2 but n can't be -ve , so n = 7

and a = 6-2n = 6-2*7 = -8

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