Question

The sum of first 10 term of a sequence whose nth trem is given by 4n-3? ​

Answer 1

the correct answer of this question is 2

Answer 2

Given :     nth term is given by 4n-3

To Find: The sum of first 10 term of a sequence

Solution:

Method 1 :

 nth term is given by 4n-3

=> aₙ = 4n- 3

a₁ = 4(1)- 3 = 1

a₁₀ = 4(10) - 3 = 37

S₁₀ = (10/2)(a₁ + a₁₀)

= 5 ( 1 + 37)

= 190

The sum of first 10 term of a sequence whose nth term is given by 4n-3

is 190

Method 2

$\sum_{n=1}^{10} (4n-3)$

$=4\sum_{n=1}^{10} n -3 \sum_{n=1}^{10} 1$

= 4 n (n + 1)/2  - 3n   where n = 10

= 2(10)(10 + 1) - 3(10)

= 220 - 30

= 190

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