Question

On a very cold morning, it was -7°F. As the day went on, the temperature rose 3 degrees each hour. Which equation shows the temperature over time?

A.y=-3x-7
B.y=-3x+7
C.y=3x-7
D.y=3x+7

Answer 1

The equation shows the temperature over time will be:

• 
  `y = 3x - 7`

Hence, option (C) is correct.

Explanation:

We know that the slope-intercept form of the line equation is

`y=mx+b`

where m is the rate of change or slope and b is the y-intercept

• Let 'y' be the temperature

• Let 'x' be the time in the hour

Given that one very cold morning, it was -7°F.

Thus, the y-intercept = b = -7

Given that as the day went on, the temperature rose 3 degrees each hour.

Thus, the rate of change = slope = m = 3

Thus, substituting m = 3 and b = -7 in the equation

`y = mx+b`

`y = 3x + (-7)`

`y = 3x - 7`

Therefore, the equation shows the temperature over time will be:

• 
  `y = 3x - 7`

Hence, option (C) is correct.