Question

If The 12th term of an A.P is −28 and 18th term is −46. Find the 1st term and comon difference

Answer 1

a+11d=-28

a+17d=-46

-5d=18

d=-18/5

Put the value of d in eq 1

Answer 2

Answer:

First term=21

Common difference=-3

Step-by-step solution

Given-

a12=-28 and a18=-46

now,

a+11d=-28                                                   eq.1

a+17d=-46                                                   eq.2

on subtracting eq.1 from eq.2 , we get

6d=-18

d=-3

now,

putting the value of d in eq.1

a+11*(-3)=-12

a-33=-12

a=-12+33

a=21

Therefore, first term(a) is 21 and the common difference(d) is -3