So for this, I will be factoring by grouping. Firstly, what two terms have a product of -4x² and a sum of 3x? That would be -x and 4x. Replace 3x with -x + 4x:

Next, factor -x² - x and 4x + 4 separately. Make sure that they have the same quantity inside of the parentheses:

Now you can rewrite the equation as

Now, apply the Zero Product Property to solve for x as such:

Your final answer is D. x = -1 and x = 4.