If the third term and the 9th term of an ap are 4 and -8 respectively which term of this ap is zero

If the third term and the 9th term of an ap are 4 and -8 respectively

1.	If the third term and the 9th term of an ap are 4 and -8 respectively which term of this ap is zero
Answer» a(3) = a + 2d4 = a\xa0+ 2da(9) = a + 8d-8 = a + 8d(elimination method)a + 2d = 4(-) a + (-)8d =(+) -8 (opposite sign)0\xa0- 6d = 12d = -2a + 2(-2) = 4 (substitution)a = 8a(n) = a + (n-1)d0 = 8 + (n-1)(-2)= 8 - 2n + 2= 10 - 2n2n = 10\xa0n = 5