If the third term of ap is 4 and ninth term of ap is -8 then which term of ap is zero

Answer 1

a+2d=4
a+8d=-8

6d=-12
d=-2

a=4-2d

a=4+4
a=8

a+(n-1)d=0

8-2(n-1)=0

4-(n-1)=0

-(n-1)=-4

n=5