Question

The temperature of a mixture is decreasing by 5∘C every hour. When it was first mixed, its temperature was recorded at −20∘C.

Which answer correctly represents the temperature of the mixture over time?


f(x)=−20x−5

That is incorrect.

f(x)=−5x−20

f(x)=−20x+5

f(x)=5x+20

f(x)=−15x

Answer 1

f(x)=−5x−20

Explanation:

It's decreasing 5 degrees every hour, which is represented by -5x

You also have to take away the 20 (-20) from where it started.

So, f(x)=−5x−20

Answer 2

f(x) = -5x - 20

Explanation:

f(x) = starting temperature + decreasing temperature * number of hours

= -20 + (-5) * x

= -20 - 5x