a At 1PM (4 hours after 9AM), the temperature is 75 degrees Fahrenheit.
B
b At m hours after 9AM, the temperature is 70 degrees.
C
c The temperature at 11AM (2 hours after 9AM) is the same as the temperature at 6PM (9 hours after 9AM).
D
d The temperature at 3PM (6 hours after 9AM) is greater than the temperature at 9AM.
Practice makes perfect
aFunction notation is one way to write functions. It explicitly shows that y is a function of x.
f(x)=y
In the given situation we have f(t)=y, where t is the number of hours after 9AM and y is the temperature at that time. We will use this to explain the meaning of the given statement.
f(4)=75
Comparing this to f(t)=y, we can see that t=4 and y=75. Therefore, the statement is telling us that 4 hours after 9AM — at 1PM — the temperature is 75 degrees Fahrenheit.
b Let's look at the given statement.
f(m)=70
Comparing this to f(t)=y, we can see that t=m and y=70. Therefore, the statement is telling us that at m hours after 9AM the temperature is 70 degrees Fahrenheit.
c Let's look at the given statement.
f(2)=f(9)
Comparing this to f(t)=y, we can see that the temperature at t=2 is equal to the temperature at t=9. Therefore, the statement is telling us that the temperature at 11AM (2 hours after 9AM) is the same as the temperature at 6PM (9 hours after 9AM).
d Let's look at the given statement.
f(6)>f(0)
Comparing this to f(t)=y, we can see that the temperature at t=6 is greater than the temperature at t=0. Therefore, the statement is telling us that the temperature at 3PM (6 hours after 9AM) is greater than the temperature at 9AM.
