Solve the problem.
-A driver wants to gauge the fuel efficiency of her vehicle at speeds of 30 mph and above. She notices that traveling at an average speed of 30 mph results in a rating of 29 mpg, where as at an Average speed of 35 mph, her car rates 19 mpg. Find a linear function f(x)= mx + b whose input is
The speed in miles per hour and whose output is the gas mileage in miles per gallon.
A) $f ( x ) = \frac { 1 } { 2 } x + 89$
B) $f ( x ) = - 2 x + 31$
C) $f ( x ) = - 2 x + 89$
D) $f ( x ) = \frac { 1 } { 2 } x + 31$

Question

Solve the problem.
-A driver wants to gauge the fuel efficiency of her vehicle at speeds of 30 mph and above. She notices that traveling at an average speed of 30 mph results in a rating of 29 mpg, where as at an Average speed of 35 mph, her car rates 19 mpg. Find a linear function f(x)= mx + b whose input is
The speed in miles per hour and whose output is the gas mileage in miles per gallon. 
A) $f ( x ) = \frac { 1 } { 2 } x + 89$
B) $f ( x ) = - 2 x + 31$
C) $f ( x ) = - 2 x + 89$
D) $f ( x ) = \frac { 1 } { 2 } x + 31$

Quizplus · Accepted Answer

The slope of the line is (19 - 29) / (35 - 30) = -2. The y-intercept is 89. So the equation of the line is f(x) = -2x + 89.

Solve the Problem f(x)=12x+89f ( x ) = \frac { 1 } { 2 } x + 89f(x)=21​x+89

Solve the Problem $f ( x ) = \frac { 1 } { 2 } x + 89$