## Algebra: A Combined Approach (4th Edition)

$3x^3+6x+x^2+2 = 3x(x^2+2) + 1(x^2+2) = (3x + 1)(x+3)$ The factor form is $(3x + 1)(x+3)$ and not $3x(x^2+2)$ because : $3x(x^2+2) = 3x^2 + 6x \ne 3x^3+6x+x^2+2$ for example $x=1$ $3x(x^2+2) = 9 \ne 12 = 3x^3+6x+x^2+2$