Final answer:
To complete the perfect square trinomial x²+4x, add 4 to get x² + 4x + 4, which equals (x+2)².
Step-by-step explanation:
To complete the perfect square trinomial x²+4x, we need to find a number that, when added to x²+4x, will create a trinomial that can be factored into (x+ )².
The process to complete the square involves taking the coefficient of the x term (which is 4), dividing it by 2, and then squaring the result.
So we have (4/2)² = 2² = 4, and the completed perfect square trinomial is x² + 4x + 4, which can be factored into (x+2)².