Question

find the sum of the first 20 terms of an a.p. whose nth term is given by an = An+B​

Answer 1

Question:

Find the sum of the first 20 terms of an a.p. whose nth term is given by an = An+B

Solution:

The sum of first 20 terms of the given sequence is 210A + 20B

Given :  

• nth term , an= An + B………….(1)

On putting n = 1 in eq 1,

• a1 = A + B

On putting n = 20 in eq 1,

• a20 = A × 20 + B
• a20 = 20A + B
• a20 = l (last term)  = 20A + B

By using the formula ,Sum of nth terms,

• Sn = n/2 [a + l]

→ S20 = 20/2 [a + l]

→ S20 = 10 [A + B + 20A + B]

→ S20 = 10 [21A + 2B]

→ S20 = 210A + 20B

Hence,

The sum of first 20 terms of the given sequence is 210A + 20B

Answer 2

Answer:

uper wala ans sahi he

Step-by-step explanation:

uper wala ans sahi he