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Question
First term and common difference of an A.P. are 1 and 2 respectively; find S10.
Given: a = 1, d = 2
find S10 = ?
Sn = `n/2 [2a + (n - 1) square]`
S10 = `10/2 [2 xx 1 + (10 - 1)square]`
= `10/2[2 + 9 xx square]`
= `10/2 [2 + square]`
= `10/2 xx square = square`
Solution
Given: a = 1, d = 2
find S10 = ?
Sn = `n/2 [2a + (n - 1)bbd]`
S10 = `10/2 [2 xx 1 + (10 - 1)bb2]`
= `10/2[2 + 9 xx bb2]`
= `10/2 [2 + bb18]`
= `10/2 xx bb20` = 100
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