Question

A bottlenose dolphin is 10 feet below sea level. Then it begins to dive at a rate of 9 feet per second. What is the equation of the line that represents its elevation, y, after x seconds?

A.
y = 9x − 10
B.
y = -9x − 10
C.
y = 9x + 10
D.
y = -9x + 10

Answer 1

B. y=-9x-10

Explanation:

The dolphin is starting 10 feet below sea level so the y-intercept (or b in slope-intercept form) would be negative 10. Diving means going down, or a negative slope, so the slope would be -9. When you plug those numbers into y=mx+b, you would get y=-9x-10.

Answer 2

B is the correct answer