SOLUTION: The fuel efficiency for a certain midsize car is given by E(v) = −0.016v2 + 1.376v + 3.8 where E(v) is the fuel efficiency in miles per gallon for a car traveling v mil

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Question 1129340: The fuel efficiency for a certain midsize car is given by
E(v) = −0.016v2 + 1.376v + 3.8
where
E(v)
is the fuel efficiency in miles per gallon for a car traveling v miles per hour.
(a) What speed will yield the maximum fuel efficiency? Round to the nearest mile per hour.______mph
(b) What is the maximum fuel efficiency for this car? Round to the nearest mile per gallon.____mpg

Found 2 solutions by rothauserc, josmiceli:
Answer by rothauserc(4718)   (Show Source): You can put this solution on YOUR website!
E(v) = -0.016v^2 + 1.376v + 3.8
:
this is the equation of a parabola that curves downward
:
velocity is plotted along the x-axis and fuel efficiency is plotted along the y-axis
:
here is a graph of E(v)
:

:
from the graph, we see that the coordinates of the vertex will give us the answers to the questions a and b
:
a. The speed(v) that will yield the maximum fuel efficiency is found from the formula
:
v = -b/2a, where b and a are from the general form for a quadratic
:
ax^2 +bx +c
:
v = -1.376/(2(-0.016)) = 43
:
*******************************************
speed for maximum fuel efficiency is 43 mph
*******************************************
:
b. substitute for v in the equation
:
E(v) = -0.016v^2 + 1.376v + 3.8
:
E(v) = -0.016(43)^2 + 1.376(43) + 3.8 = 33.384 is approximately 33
:
****************************************************************
The maximum fuel efficiency for the car is 33 miles per gallon
****************************************************************
:

Answer by josmiceli(19441)   (Show Source): You can put this solution on YOUR website!
The formula for the v-value of the vertex is:
where




(a)
43 mi/hr gives maximum fuel efficiency
(b)




The maximum fuel efficiency for the car is 33 mi/gal
( check my math )
------------------
Here's the plot of the equation:

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