Question

At 5 a.m., the temperature at an airport was −9.4°F . Six hours later, the temperature was 2.8°F . Which expression represents the total temperature change over the six hours?

Answer 1

|2.8 - (-9.4)|

Explanation:

The correct answer is |2.8 - (-9.4)|.

Answer 2

Let x = the number of hours since 5 a.m.
Let y = temperature, °F

Let the total temperature change be modeled by the expression
y = ax + b

At 5 a.m., x = 0 and y = -9.4°F. Therefore
b = -9.4

When x = 6 hours, y = 2.8°F. Therefore
6a + b = 2.8
6a - 9.4 = 2.8
6a = 12.2
a = 2.0333

The expression is
y = 2.0333x - 9.4

Answer:
y = 2.0333x - 9.4
where
x = hours since 5 a.m.
y = temperature, °F