the sum of n terms of the series is given by Sn= n^2-5n. which term of the series is 50
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Answer:
nswer
S
n
=3n
2
+7−5n
t
n
=S
n
−S
n−1
=(3n
2
−5n+7)−[3(n−1)
2
−5(n−1)+7]
=3n
2
−5n+7−[3(n
2
−2n+1)−5n+5+7]
=3n
2
−5n+7−3n
2
+6n−3+5n−12
=6n+7−3−12
t
n
=6n+7−15
t
n
=6n−8
so,
t
2
=6×2−8=4
t
7
=6×7−8=42−8=34
t
8
=6×8−8=48−8=40
t
10
=6×10−8=60−8=52
thus,
t
7
=34 and t
8
=40 are correct options.
mjhere1512:
Do u take me for a fool
its not the correct ans
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