Here is what I am trying to factor:

2x^2 + 3x + 1 = 0.

I split the middle term.

2x^2 + 3x - 1x + 1

Then grouped them.

(2x^2 +3x) + (-1x + 1)

Here is where I am having the problem. What should I do next?

Thank you! :-)

You did not split the middle term, you added a term "out of the blue".

The numbers to use to split the middle term are 2 and 1. When multiplied together, they give 2 (that is the product of a and c), and when added together they give 3 (that is b).

2x^2 + (2x + 1x) + 1 = 0

regroup
(2x^2 + 2x) + (1x + 1) = 0

pull out the GCF from each parentheses.
2x(x + 1) + 1(x + 1) = 0

not pull out the common factor (x + 1)
(x + 1)(2x + 1) = 0

see if you can take it from there.