Answer:
They sold 120 milkshakes that day
Step-by-step explanation:
We can set up a proportion


Note: If you have some value,
, and it is
of the total amount, you can find the value by doing the equation 
Let y be the temperature
Let m be the rate of temperature drop in degrees per hour
Let x be the number of hours elapsed since 8PM
The initial temperature (at x = 0) is 0
y = mx
Four hours from 8 PM, the temperature was -16.8 degrees
-16.8 = m(4)
m = -4.2 degrees per hour
At 9PM, one hour will have elapsed.
y = -4.2(1)
y = -4.2 degrees
Answer:
The given function is a nonlinear function because the degree of the function is 2 and we get same value of y for more than one values of x.
Step-by-step explanation:
The given function is

To find the points which lie on the function, put difference values of x in the given function and find the values of y.
Put x= -2

Put x= -1

Put x= 0

Put x=1

Put x= 2

The table of values is shown below.
Plot these points on a coordinate plane and connect them by a free hand curve.
The given function is a nonlinear function because the degree of the function is 2 and we get same value of y for more than one values of x.
The graph of function is shown below.