Question

If 3rd and 9th term of an A.P. are 4 and -8 respectively then which term of its will be zero?​

Answer 1

Answer:

given t3=4

=>a+2d=4 ------ 1

and t9=-8

=>a+8d=-8 -------2

on doing equations 1-2

we get -6d=12

d=12/-6=-2

on substitution of d in equation 1 we get

a=8

now

tn=0

a+(n-1)d=0

8+(n-1)*-2=0

(n-1)*-2=-8

(n-1)=-8/-2

(n-1)=4

n=5

so 5th term of ap is 0