split it up an group with like ones (6x^3 with 2x since 6 and 2 are divisble by 2 and 9x^2 with 3 since both divisible by 3)
(6x^3+2x)+(9x^2+3)
undistribute using reverse distributive property (ab+ac=a(b+c))
2x(3x^2+1)+3(x^2+1)
undistribute again
(3x^2+1)(2x+3)