Find the 19th term of an A.P. -11,-15,-19,...
Solution :
nth term of the A.P
tn = a + (n - 1)d
a = -11 , d = -15 - (-11) = -15 + 11 ==> -4
t19 = -11 + (19 - 1)(-4)
= -11 + 18(-4)
= - 11 - 72
t19 = -83
Therefore, the 19th term of the A.P. is -83.