Question

Select the correct answer.
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

Reason: initial elevation y(0) = −10 (10 ft below sea level) and diving decreases elevation at 9 ft/s, so slope = −9.