Which set of numbers can represent the side links in centimeters of a right triangle

Look at the following graph of the given equation. determine whether the equation is a function. explain why or why not.

Eric has challenged himself to walk 24,000 steps in 4 days. if eric walks the same number of steps each day, which function represents the number of steps eric still needs to walk to reach his goal with respect to the number of days since he started his challenge? a. y = 8,000x − 24,000 b. y = -8,000x + 24,000 c. y = 6,000x − 24,000 d. y = -6,000x + 24,000

Ineed to know the answer to this algebra question.