Question

The function f(x) = −x2 − 5x + 50 shows the relationship between the vertical distance of a diver from a pool's surface f(x), in feet, and the horizontal distance x, in feet, of a diver from the diving board. What is a zero of f(x), and what does it represent?
A x = 5; the diver jumps in the pool at 5 feet per second
Bx = 10; the diver jumps in the pool at 10 feet per second
C x = 10; the diver hits the water 10 feet horizontally from the board
Dx = 5; the diver hits the water 5 feet away horizontally from the board

Answer 1

First of all, the root is $5$, since

$-5^2-5\cdot 5 + 50 = -25-25+50=0$

Then, since the $x$ represents the horizontal distance, and $f(x)$ the height, we can read $f(5)=0$ as "the height is zero when the diver is $5$ feet away from the board.

So, the answer is D.