Question

if in AP 15 term is 9 and 9 term is 15 find the 20th term​

Answer 1

a=Answer:

a15=9

a+14d=9

a=9-14d

a9=15

a+8d=15

9-14d+8d=15

-6d=6

d=-1

a+14(-1)=9

a-14=9

a=23

a20=a+(20-1)d

a20=23-19

a20=4

Step-by-step explanation:

Answer 2

Answer:

20th term = 4

Step-by-step explanation:

15th term = a + 14d = 9

9th term = a + 8d = 15

15th term - 9th term

a + 14d = 9

- (a + 8d = 15)

a + 14d - a - 8d = 9 - 15

6d = -6

d = -6/6 = -1

substitute d in 9th term

a + 8(-1) = 15

a - 8 = 15

a = 15 + 8

a = 23

20th term = a + 19d

= 23 + 19(-1)

= 23 - 19

= 4

hope you get your answer