Respuesta :

irspow
Rearranging slightly you see:

3x^3+x+3x^2+1  now factor 1st and 2nd pair of terms...

x(3x^2+1)+1(3x^2+1)

(x+1)(3x^2+1)
ghanami
hello : here is a solution
 3x^3+x+3x^2+1 = 3x²(x+1)+(x+1) = (x+1)(3x²+1)