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

Answer: The correct option is (D) y = 2x - 8.

Step-by-step explanation:  Given that the temperature was -8°F on a very cold morning. And, it goes on increasing by 2° each hour.

We are to select the correct equation that shows the temperature over time.

Let, 'x' represents the number of hours increasing one by one and 'y' be the temperature in degree fahrenheit in the x-th hour.

So, at x  = 0, y = -8,

and at x = 1, y = -8 + 2 = -6.

Therefore, (x, y) = (0, -8) and (1, -6).

So, slope of the line representing the relation between 'x' and 'y' is

$m=\dfrac{-6+8}{1-0}=2.$

Hence, the equation of the line will be

$y-(-8)=m(x-0)\\\\\Rightarrow y+8=2(x)\\\\\Rightarrow y=2x-8.$

Thus, (D) y = 2x - 8 is the correct equation.

Answer 2

2x-8 is the answer, hope this helps