Find Decreasing Intervals of the Quadratic Function y = (x-4)² - 4

To determine the interval where the function $y = (x-4)^2 - 4$ is decreasing, we need to analyze its vertex form and the parabola's properties:

1. The function is in the vertex form $y = (x-4)^2 - 4$, where $(h, k) = (4, -4)$.

2. Since the quadratic function is opening upwards (as $a = 1 > 0$), it means the derivative of the function is negative to the left of the vertex, indicating decreasing behavior for $x < h$.

3. For $y = (x-4)^2 - 4$, the vertex is at $(4, -4)$, so the function is decreasing for all $x < 4$.

Therefore, the interval where the function is decreasing is $x < 4$.