Sn=n(n+1)÷२ then sn=276 find the n
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Sn=n(n+1)÷2
276=n(n+1)÷2
276×2=n(n+1)
552=n^2+n
n^2+n-552=0
n^2+24n-23n-552=0
n(n+24)-23(n+24)=0
(n-23)(n+24)=0
n=-24 or n=23
here -24 is neglected as it is negative and n term can't be negative
Hence, n=23
276=n(n+1)÷2
276×2=n(n+1)
552=n^2+n
n^2+n-552=0
n^2+24n-23n-552=0
n(n+24)-23(n+24)=0
(n-23)(n+24)=0
n=-24 or n=23
here -24 is neglected as it is negative and n term can't be negative
Hence, n=23
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