in an a.P if thr 12th trarm is_13and the sum of its first 4term is 24 .Find the sum of its first 10 term
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12th term,a+11d=-13-----(1)
sum of 1st 4th term,a+a+d+a+2d+a+3d=24
=>4a+6d=24
=>2a+3d=12-----(2)
(1)×2-(1)=>19d=-38
=>d=-2
(2)=>2a=18
a=9
10th term,a+9d=9-18=-9
sum of 1st 10 term is=10/2×[9-9]
=0
sum of 1st 4th term,a+a+d+a+2d+a+3d=24
=>4a+6d=24
=>2a+3d=12-----(2)
(1)×2-(1)=>19d=-38
=>d=-2
(2)=>2a=18
a=9
10th term,a+9d=9-18=-9
sum of 1st 10 term is=10/2×[9-9]
=0
singhvipul58:
thank
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