Question

If the third and ninth terms are



a.P are 4 and -8 then which term of this



a.P is zero

Answer 1

Answer:

5th term

Step-by-step explanation:

nth term = a+(n-1)d

3rd term = a+(3-1)d = a+(2)d = 4 ----(1)

9th term = a+(9-1)d = a+(8)d = -8 ----(2)

(1)×4 = 4a+(8)d = 16

(1) - (2) = 3a = 24 =>> a = 8

8+2d = 4 =>> 2d = -4 =>> d = -2

a+(n-1)d = 0

8+(n-1)-2 = 0

(n-1)-2 = -8

(n-1) = 4

n = 4+1 = 5