Answer
$ (7x^2+3)(4x-1)$
Work Step by Step
$28x^3-7x^2 +12x-3= 7x^2(4x-1) + 3(4x-1)$
The binomial $(4x-1)$ is present in both terms and is the greatest common factor. We use the distributive property to factor out $(4x-1)$
$28x^3-7x^2 +12x-3= 7x^2(4x-1) + 3(4x-1) = (7x^2+3)(4x-1)$