What is the quadratic formula of 4,12,36

Answer 1

No idea what you are talking about.
if 4, 12, 36 are the roots, you would have a cubic.
if the 3 numbers are the a,b, and c of ax^2 + bx + c = 0
then the equation would simply be 4x^2 + 12x + 36 = 0
or
x^2 + 3x + 9 = 0
x = (-3 ± √-27)/8

Answer 2

if you mean a geometric sequence,
an = 4*3^(n-1)