Solve for x>0 in the following arithmetic sequence 1^2,x^2,3^2.....
1 , x^2 , 9
x^2 - 1 = d
-x^2 + 9 = d
---------------
0 + 8 = 2 d
d = 4
so
1 , 5 , 9
x = sqrt(5)
x^2 - 1 = d
-x^2 + 9 = d
---------------
0 + 8 = 2 d
d = 4
so
1 , 5 , 9
x = sqrt(5)