Question

7. Determine the AP whose third term
is 15 and seventh term is 23.
​

Answer 1

Answer:

AP: 11; 13; 15 ; 17;........23

Answer 2

The required AP is 4 ,10 ,16 ,22 ,28 ,34 ,40......

Step-by-step explanation:

Let a be the first term,a3 be the third term, a5 be the fifth term and a7 be the seventh term

we know that : an=a+(n-1) *d

a3 = 16 [given]

a+(3-1)*d=16

a+2d=16...........(I)

Now a7-a5=12 [given]

[a+(7-1)d] -[a+(5-1)d] =12

2d=12

d=12/2

d=6

From eq. (1) we get,

a+2(6) =16

a+12=16

a=16-12

a=4

so, first term, a is 4

we can find AP by adding d continuously

so, the required AP is 4 , 16 , 22 , 28 , 34 , 40......