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Given an = 4, d = 2, sn = -14 find n and a |
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Answer» a=-8 n=7 an= a+(n-1)d4=a+2n-24+2=a+2n6=a+2n6-2n=aNow, Sn= n/2(a+an)-14=n/2(6-2n+4)-14=n/2(10-2n)-28=10n-2n²2n²-10n-28=02(n²-10n-14)=0Then solve urself a=-8,10 |
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