Question

On a very cold morning, it was -8°F. As the day went on, the temperature rose 2 degrees each hour. Which equation shows the temperature over time?

A) y = -2x + 8


B) y = -2x – 8


C) y = 2x + 8


D) y = 2x – 8

Answer 1

you start with -8 then rise 2 per hour, so this would be +2x.

D. y = 2x - 8

Answer 2

Answer:

D) y = 2x – 8

Step-by-step explanation:

In this problem, the initial condition is -8, because the start of the day, the morning, was -8 °F. This characteristic is really important, initial condition are expressed as y-interception, which is the constant term of a linear function.

So, in this case, the viable answers are B or D, it depends on the ratio of change.

The problem states that as the day went on, the temperature ROSE 2 degrees each hour, that expressed an increasing behaviour of 2. Mathematically, that means the independent variable must be negative.

Therefore, the right answer is D., because it has a positive rate of change, and it has -8 as y-interception or initial condition.