To determine how far the firework will travel before it reaches the ground, we need to solve the quadratic equation given by the height function:
\[ 0 = -x^2 + 15x. \]
We can rearrange this equation:
\[ -x^2 + 15x = 0. \]
Next, we can factor out \( x \):
\[ x(-x + 15) = 0. \]
Now we can set each factor equal to zero:
- \( x = 0 \)
- \( -x + 15 = 0 \) → \( x = 15 \)
The solutions to the equation are \( x = 0 \) and \( x = 15 \). The solution \( x = 0 \) represents the position at launch, and \( x = 15 \) feet represents the horizontal distance traveled before the firework reaches the ground.
Therefore, the firework will travel 15 feet before it reaches the ground.
Answer: 15 feet