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The sum of the series 11-3 12+14+ 21-3 22+24+ 31-3 32+34+ up to 10-terms is
(2) - 55109
Tr= rr4-3r2+1= r(r2-1)2-r2
= r(r2-r-1)(r2+r-1)
(r2+r-1)-(r2-r-1)=2r
Tr= 12 [ 1r2-r-1- 1r2+r-1 ]
r2+r-1=(r+1)2-(r+1)-1, the terms telescope
S10= 12 [ 11-1-1- 1100+10-1 ]= 12 [-1- 1109 ]
=- 55109
Answer: (2)
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