Use the grouping method to factor the polynomial below completely.
3x3 + 9x2 + 5x + 15

(3x^2+5)(x+3)

Step-by-step explanation:

The given expression is:

3x3 + 9x2 + 5x + 15

First of all group the first two terms and last two terms:

(3x3 + 9x2) + (5x + 15)

Now factor out the greatest common factor from each group:

3x^2(x+3)+5(x+3)

(3x^2+5)(x+3)

Thus the factors of 3x3 + 9x2 + 5x + 15 are:

(3x^2+5)(x+3)