Question

which term of the AP:5,2,-1 .......is -49​

Answer 1

a = 5

d = a2-a1 = 2-5 = -3

an = 49

n =?

an = a+(n-1)×d

-49 = 5+(n-1)×-3

-49 = 5+(-3n+3)

-49 = 8-3n

-49-8 = -3n

-57 = -3n

-57/-3 = n

+19 = n

as our theory

- ×/÷ - = +

- ×/÷ + = -

+ ×/÷ + = +

answer : n = 19

Answer 2

19 term will be -49

Explanation:

from A.P. formula,

-49 = 5+(n-1) -3

-49-5 = (n-1)-3

-54 = (n-1)-3

-54/-3 = n-1

18 = n-1

18+1 = n

N = 19