Hello,
The temperature changes at rate of -1.5 degree celsius every hours and the reading of temperatures starts at 0 degree celsius which can be modeled into the linear equation of f(t) = -1.5t where f(t) is the temperature function and t is time.
The problem then asks, “what was the temperature 7 hours ago?” This question asks for the temperature 7 hours ago which means t = -7 in this case since we are solving for temperature 7 hours ago, not next 7 hours.
Time being negative in this scenario means in past or hours ago, generally time cannot be negative as it’s scalar quantity.
Substitute t = -7 in the temperature function, this’ll result in:
- f(-7) = -1.5(-7)
- f(-7) = 10.5
Therefore, 7 hours ago, the temperature was at 10.5 degree celsius. Please let me know if you have any questions!