Answer:
Increasing: (2, ∞) Decreasing: (-∞,2)
Explanation:
Think of the parabola (just for visualization purposes) as the direction of a rubber ball being thrown from above. The ball starts to decrease in position, eventually hitting the ground, and then starts to increase back to the orginal height and beyond.
So, because parabolas extend infinitely in both the positive and negative direction, we can use intervals to express the parts of the graph where it increases and decreased.
The minimum value point, or vertex is the point where the parabola changes direction. The vertex is visibly at (2,-4). So, the interval for decreasing would be (-∞,2) and increasing would be (2,∞)
Note: We use the symbol "[" to indicate that a value is included in the interval.
Because infinity is a concept and not a number, we have to use the non-inclusive version of it: "(" (simple parentheses) to indicate that infinity is NOT included in the interval, but it simply keeps extending in both directions.
I hope this helps you out.