Given that,a3=4a9=−8We know that,an=a+(n−1)da3=a+(3−1)d4=a+2d……(i)a9=a+(9−1)d−8=a+8d……(ii)On subtracting equation (i) from (ii), we get,−12=6dd=−2From equation (i), we get,4=a+2(−2)4=a−4a=8Let nth term of this A.P. be zero.an=a+(n−1)d0=8+(n−1)(−2)0=8−2n+22n=10n=5Hence, 5th term of this A.P. is 0.