Question

find the sum of first 28 terms of an a.pwhose nth term is 4n-3​

Answer 1

Answer:

1540

Step-by-step explanation:

nth term of AP a(n) = 4n - 3

First term ( l ) = a(1) = 4( 1 ) - 3 = 4 - 3 = 1

Last term ( l ) = a(28) = 4( 28 ) - 3 = 112 - 3 = 109

Sum of first 28 terms = S(8) = n / 2 × ( a + l )

⇒ S(28) = 28/2 × ( 1 + 109 )

⇒ S(28) = 14 × 110

⇒ S(28) = 1540

Therefore the sum of 28 terms of an AP is 1540.