For this case we have the following system of equations:
We multiply the first equation by -4:
We have the following equivalent system of equations:
We add the equations:
We find the value of the variable "x":
Thus, the solution of the system is:
See the graphic in the attached image
ANswer:
See the graphic in the attached image
Answer:
a) In the interval of [1980,1983].
b) In the interval of [1991, 1996].
Step-by-step explanation:
Fuel efficiency:
The fuel efficiency, for the cars, in x years after 1980, is given by:
15.9 is the fuel efficiency in 1980.
a. In what years was the average fuel efficiency for cars less than 17 mpg (in interval form)?
From 1980 to:
3.06 = 1980 + 3 = 1983. So
In the interval of [1980,1983].
b. In what years was the average fuel efficiency for cars more than 20 mpg (in interval form)?
From x until 1996.
11.38 = 1980 + 11 = 1991. So
In the interval of [1991, 1996].