Question

I need all the formulas of chapter 9; Sequences and series; class 11th

Answer 1

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Answer 2

1) first term = a and common difference = d

Tn = a + ( n - 1 )d

2) Sum of n terms with first term = a and last term = l

Sn = n/( a + l)

3) sum of n term with common difference and first term

Sn = n/2 { 2a + ( n - 1 )d }

4) The Arithmetic mean b/w a and b is a + b/2

5) In G.P with first term and common ratio

nth term = ar^n - 1

6) In GP Sn = a(1 - r^n)/( 1 - r ) , when r < 1

Sn = a(r^n -1)/(r - 1 ) , when r > 1

7) G.M b/w a and b = √ab

8) ( 1 + 2 + 3 + 4 + 5.......) = 1/2n(n + 1)

9) (1^2 + 2^2 + 3^2 + 4^2+ 5^2 .....) = 1/6n(n+1)(2n+1)

10) 1^3 + 2^3 + 3^3 + 4^3 + .......) = {I/2n(n+1)}^2