Final answer:
The expression 4x^2 + 4x can be factorized by extracting the greatest common factor, resulting in the factored form 4x(x + 1).
Step-by-step explanation:
The expression provided seems to contain some typos, but based on the context of the given references and typical algebraic procedures, it appears that the task is to factorize a quadratic expression.
To factorize the expression 4x^2 + 4x, we can first factor out the greatest common factor (GCF), which is 4x in this case:
4x^2 + 4x = 4x(x + 1).
Now, the expression matches the pattern of the original question where the blank can be filled in. The factored form of the expression is therefore 4x(x + 1).