Question

please give a correct solution of

Answer 1

Second number is = a - 1

Third number = a + 1

First number = a

a + a - 1 + a + 1 = 21

3a = 21

a = 7

First number = 7

second number = 6

Third number = 8

Answer 2

let terms of ap is a-r,a,a+r
a-r+a+a+r=21 (given)
a= 7
now,
a-r,a-1,(a+r+1) are in gp (given)
(a-1)^2 =(a-r)(a+r+1) [gm]
by putting value of a= 7 ,we get
r=4 or -5
thus numbers are (3,7,11) &(12,7,2)