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Find the sum to n terms of the A.P.5,2,-1,-4,-7...
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a= 5
d= 2-5 = -3
Sn = n/2 (2a+ (n-1)-3)
= n/2 (10+n-1-3)
= n/2 (6+n)
= 6n+n^2/2
d= 2-5 = -3
Sn = n/2 (2a+ (n-1)-3)
= n/2 (10+n-1-3)
= n/2 (6+n)
= 6n+n^2/2
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