The total cost c(x) of hiring a dump truck and an operator is described by the function c(x)=300+31x-3.90x^2 , where x is the number of hour

Question

The total cost c(x) of hiring a dump truck and an operator is described by the function c(x)=300+31x-3.90x^2 , where x is the number of hours worked. Find the number of working hours if c(x)=$220.

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Thu Cúc 5 months 2021-08-31T10:40:15+00:00 1 Answers 5 views 0

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    2021-08-31T10:41:53+00:00

    Answer:

    2.05hrs

    Step-by-step explanation:

    Given he total cost c(x) of hiring a dump truck and an operator is described by the function c(x)=300+31x-3.90x^2 , where x is the number of hours worked. If c(x)=$220, then;

    220  = 300+31x-3.90x^2

    300+31x-3.90x^2 – 220 = 0

    3.90x^2 + 31x – 80 = 0

    x = -31±√31²-4(-80)(3.9)/2(3.9)

    x = -31±√961+1.248/7.8

    x = -31±47/7.8

    x = -31+47/7.8

    x = 16/7.8

    x = 2.05

    hence the number of working hours is 2.05hrs

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