Question

if the nth term of an a.p. is(2n+1), find the sum of first n term of the a.p.

Answer 1

Hey !!!

nth term of an A.P is (2n+ 1 )

Hence,

a₁ =2 * 1 + 1

a₁= 3

similarly ,

a₂ = 2* 2 + 1

a₂= 5

∵ d = a₂ - a₁ = 5 - 3 =2

we know that the sum of nth term of an AP

sₙ = n/2 { 2a + (n - 1 ) d}

putting the value of given term.

sₙ = n/2 { 2 * 3 + ( n - 1 ) 2

sₙ = n ( 3 + ( n - 1 )

sₙ = 3n + n² - n

sn = n² + 2n Answer

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Hope it helps you !!!

@Rajukumar111