A linear model changes by the same amount for each unit of input. If a question gives the time and asks for the temperature, time is the input: substitute it into the rule, then evaluate the rule in Desmos. Don’t multiply the starting temperature by the time; only the hourly change repeats.
Hints
- Hint 1
An input is the number you put into a rule. Here, time is the input and temperature is the output. Which letter in the equation should take the given number of hours?
- Hint 2
In a linear model, the term without is the starting temperature. The number multiplying is the hourly change. Multiply that change by the number of hours, then combine it with the start.
Step-by-step
Substitute the time
Step 1Turn four hours into an input
The question asks for the temperature after hours, so put in for the time : . Substitute the time for , not for . The is the starting temperature; only the hourly decrease of is multiplied by .
- Step 2
Evaluate the temperature
Type in Desmos, then type . Desmos prints , so the liquid’s temperature after four hours is degrees Fahrenheit. Choice D.