Answer:
a) 29.50 miles per gallon b) 29.87 miles per gallon c) 28.19 miles per gallon
Step-by-step explanation:
A specific car fuel economy (miles/gallon) = f(x) = 0.00000056x^4 - 0.000018x^3 - 0.016x^2 + 1.38x - 0.38
where x represents the car speed in miles per hour.
when x = 40 miles per hour
A specific car fuel economy (miles/gallon) = f(x) = 0.00000056(40)^4 - 0.000018(40)^3 - 0.016(40)^2 + 1.38(40) - 0.38 = 1.4336 - 1.152 - 25.6 + 55.2 - 0.38 = 29.50 miles per gallon
Similarly,
when x = 50
A specific car fuel economy (miles/gallon) = f(x) = 0.00000056(50)^4 - 0.000018(50)^3 - 0.016(50)^2 + 1.38(50) - 0.38 = 3.5 - 2.25 - 40 + 69 - 0.38 = 29.87 miles per gallon
Similarly,
when x = 60
A specific car fuel economy (miles/gallon) = f(x) = 0.00000056(60)^4 - 0.000018(60)^3 - 0.016(60)^2 + 1.38(60) - 0.38 = 7.26 - 3.89 - 57.6 + 82.8 - 0.38 = 28.19 miles per gallon
