Question

if 21,a,b,-3 are in ap find value of a+b

Answer 1

If the given series is in arithmetic progression, then their is a common difference between the consecutive terms. Here 'd' is the common difference.
i.e 21+d=a
So the first equation is d=a-21
i.e b+d=-3
So the second equation is d=-3-b
All together third equation is a-21=-3-b=d
Let's neglect 'd' as we don't know the value
So the final equation is
a-21=-3-b
a+b=21-3
Therefore the value of a+b is 18

Answer 2

Answer:

a-21=d

eqn1 where d is the common difference of AP

b-a=d eqn2

-3-b=d eqn3

RHS OF EQN 1 and 3 are same so a-21=-3-b so a+b=-3+21=18

Step-by-step explanation:

BTS ARMY