Question

IF A =(3,9, 20, 21), Than write An
the set builder form​

Answer 1

Answer= 3

Step-by-step explanation:

When x is added to 3, 9, 21then we get

3+X ,9+ X. 21+x

If these are in GP then

(9+x)/(3+x)=(21+x)/(9+x)

i.e.

(9+x)(9+x)=(3+x)(21+x)

or 81+18x+x^2=63+24x+x^2

or6x=18

x=3