the sum of the first 41 term of an A.P in 5125 .find the value of 21st term
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A.T.Q
a²¹ =a+20d
25=a+20d
a =25-20d
Then,
S⁴¹=41/2[2a +40d]
=41/2[2(25-20d)+40d]
=41/2[2(25-20d)+2(20d)]
=41/2×2(25-20d+20d)
=41(25)
=1025. Ans
arunadeshmane75:
thanks
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