Question

sum of first and 5th term of AP is 18 and 14th term exceeds twice first term by 2 find the sum of first twenty terms

Answer 1

Answer:

30

Step-by-step explanation:

Let a be the first term and d be the common difference

a + 13d - 2a = 2

-a - 13d = 2                              - 1

a + A5 = 18

a + a + 4d = 18

a +2d = 9                               - 2

From 1 and 2

-11d = 11

d = -1

Substituting d = -1 in 2

a -2 = 9

a = 11

S20 = 20[2a + 19d]/2

       = 10[22 -19]

       = 30