Question

an=n2+2n−1 first four tearms​

Answer 1

Step-by-step explanation:

Given :-

$a_n = {n}^{2} + 2n - 1$

To find :-

• first four terms

Using the given condition,

Putting n = 1

$a_1 = {1}^{2} + 2(1) - 1$

$\implies \: 1 + 2 - 1$

$\implies \: \boxed{ a_1 = 2}$

Putting n = 2

$a_2 = {2}^{2} + 2(2) - 1$

$\implies \: 4 + 4 - 1$

$\implies \: \boxed{a_2 = 7}$

Co m mon dif fer ence,d = 7-2 = 5

Now four terms of AP are,

$\implies \: a - 2d,a - d,a + d,a + 2d$

$\implies2 - 2(5),2 - 5,2 + 5,2 + 2(5)$

$\boxed{ - 8, - 3,7,12}$