Question

Find the ap whose fourth term is 9 and sum of its sixth term and thirteenth term is 40

Answer 1

Hey

Here is your answer,

given that,

a4 =9 a6 + a13 =40

we can write,

a+3d=9.._------(i)

a+5d+a+12d=40

2a+17d=40-------(ii)

multiplying..eq. (i) with 2..and subtracting it from eq. (ii)

2a+6d=18

2a+17d=40

_ _ _

_____________

-11d= -22

D=2

now putting he value of d in eq..(i) we get,

a + 3d=9

a +3(2)=9

a+6=9

A=3

now...AP form will be..

3,5,7,9,11--------

Hope u get it..!