Consider the following AP sequence: 134, 104, 74,… The 6thterm is
the first negative term
In the given AP; a1=134;d=−30
an = a1 + (n-1)d ⇒ a6 = 134 + (6-1)(-30) = -16 and this term is negative.
a5 = 134 + (5-1)(-30) = 14
Till the fifth term, the terms are all positive. So the sixth term, which is -16 is the first negative term.