This is of the form ax^2+bx+c. To factor a quadratic like this you want to find two values, j and k, that satisfy two conditions.
jk=ac and j+k=b...in this case:
jk=ac=36 and j+k=b=12, so j and k must be 6 and 6
Now you replace bx with jx and kx in the original equation which gives you:
9x^2+6x+6x+4 now factor the first and second pair of terms...
3x(3x+2)+2(3x+2) which is equal to:
(3x+2)(3x+2) which is just:
(3x+2)^2
