Question

If 9th term is 75 and 21th yearn is 185 find 81th term of an A.P .

Answer 1

Answer:

81 TERM IS 795

Step-by-step explanation:

a n = a1 +(n-1) d                      (A)

75=a1+(9-1)d             (i)

185 = a1+(21-1)d        (ii)

by two equation we get value of a and d

we get d=10 and a = -5

putting these value in  eq A we get

a81=-5 +80 *10

a81 = -5 +800

=795