Question

find the number of terms in this ap18,31/2,13... an=-47​

Answer 1

Answer:

d = 31-18 = 13

an = 18 + (n-1)13

-47 - 18 = (n-1)13

-65 = (n-1)13

-65 = 13n - 13

-65+13 = 13n

- 52 = 13 n

n = -52/13

n = -4

Answer 2

Answer:

n=27

Step-by-step explanation:

a= 18 , d= 31/2 - 18 = 31-36/2 = -5/2

now, an=-47

a+(n-1)d = -47

18+ (n-1)( -5/2 ) = -47

(n-1)(-5/2)= -65

n-1= -65 x 2/-5

n-1 = 13 x 2

n-1= 26

n= 27