Question

If 21 , a , b and -3 are in AP then find the value of (a+b)

Answer 1

Answer:

If 21 , a , b and -3 are in AP

we know

a2-a1 = a3- a2 = a4-a3 = d = common difference

a - 21 = b - a = -3 - b

from here we get

a - 21 = -3 -b

a+ b = 21-3

a + b = 18

Answer 2

Answer:

As the sequence is in AP hence,

As the sequence is in AP hence,a-21=b-a=-3-b

which can be also written as

a-21= -3-b

a+b= 21-3

a+b=18