If sum of n terms of an A. P. Is 10n-n^2 then find the 7th and 11 term
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S1 = 10x1-1'2 = 9
:a1 = 9
S2 = 10x2-2'2= 16
:a2 = S2-S1 = 16-9 = 7
S3= 10x3-3'2 = 21
:a3= S3-S2 = 5
:> A.P. = 9,7,5......
A'7 = 9 + 6x-2 = -3
a'11 = 9 + 10X -2 = -11
Pp147:
Thank you for the answer
Wlcm
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