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.