Answer:
[tex](x + 2)(5x + 2)[/tex]
Step-by-step explanation:
What we would normally do when factoring a polynomial is find the greatest factor, but in this case, there is none. What we do then is multiply the coefficient of the first term by the last term.
So in this case, that expression would be...
[tex]5 * 4 = 20[/tex]
Then, we have to find two factors of 20 that, when added together, equal the second term's coefficient (12).
These factors would be 2 and 10.
[tex]2 * 10 = 20\\\\2 + 10 = 12[/tex]
We then replace the second term in the polynomial with [tex]10x + 2x[/tex]. This ends up looking like this:
[tex]5x^2 +10x + 2x +4[/tex]
Keep in mind that this did not change the value of the polynomial, as 10x + 2x still equals 12x.
This new expression lets us use a technique called group factoring. To start group factoring, we need to take out the greatest common factor (GCF) of the first two terms. That ends up looking like this:
[tex]5x(x + 2)[/tex]
Then, we do the same thing with the last two terms.
[tex]2(x + 2)[/tex]
We know we're on the right track at this point, because the expressions inside the parenthesis in both GCFs are the same.
The last step is combining the terms on the outside of the parenthesis, and multiplying it with what's inside the parenthesis. The final answer looks like this.
[tex](x + 2)(5x + 2)[/tex]
