Factor 12a^3+4a^2+3ab+b

$12 a^{3} + 4 a^{2} + 3 a b + b$

Factor out the greatest common factor from each group.

Group the first two terms and the last two terms.

$(12 a^{3} + 4 a^{2}) + 3 a b + b$

Factor out the greatest common factor (GCF) from each group.

$4 a^{2} (3 a + 1) + b (3 a + 1)$

Factor the polynomial by factoring out the greatest common factor, $3 a + 1$ .

$(3 a + 1) (4 a^{2} + b)$