Functions: Evaluate F(-3) = 4x^2-3x-5; find linear fcn; etc.

dv8anly

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Feb 5, 2008
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Just want to check and see if I'm on the right track,

1. Evalyate F(-3) = 4x^2 - 3x - 5,
F(-3) = 4(9) - (9) - 5
F(-3) = 36 - 4 = F(-3) = 32

2. The value of a computer after t years is given by the depreciation function V(t) = $2000 - 150t. Waht is the value of the computer 4 years after it is purchased? V(t) = $2000 - 150t =
V(4) = $2000- $600=
V(4) =$1,400.
3. A cab company advertises $0.45 per mile (or part of a mile) plus a $2.00 minimum charge. Based on this information, write a linear function that describes the price of a cab ride in terms of the miles travled. C(m) = $0.45 + $2.00

4. If a customer travels a total of 25 miles, how much money will that customer owe the cab company in question 3? C(25) = 25(0.45)+ $2.00 = $13.45

5. The future of a population of a town t years after January 1, 1995 is described in thousands by function P(t) = 120 + 4t + 0.05t^2. Calculate of P(5) and explain what it means. P(5) = 120 + 4t + 0.05t^2,
P(5) = 120 + 20 + 1.25 = 14,125
It means that the future population of a town will be 14,125 after January 1, 1995

6. The gravitational force between two objects varies inversely as the square of the distance between the objects. If a force of 25 pounds results from two objects that are 6 miles apart, how much force results from two objects that are 15 miles apart? 25 = 6 = 4.166(15) = 62.5

7. The population of Windham is growing at an annual rate of 0.5%. If the current population 12,520, one function that can be used to predict the future population of Windham is P(t) = 12,520(1.005)^t where t represents times in years. Use this function to predict the population of Windham in 10 years. P(10) = 12,520(1.005)10
P(10) = 125,826
 

Loren

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Aug 28, 2007
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1,299
Re: Functions

1. Evalyate F(-3) = 4x^2 - 3x - 5,

I guess you mean F(x) = 4x^2 -3x - 5

F(-3) = 4(9) - (9) - 5 <-- should be F(-3) = 4(-3)^2 - 3(-3) -5 = 4(9) + 9 - 5 Now, you take it from there.

2. Looks good.

3. A cab company advertises $0.45 per mile (or part of a mile) plus a $2.00 minimum charge. Based on this information, write a linear function that describes the price of a cab ride in terms of the miles travled.

C(m) = $0.45 + $2.00 <-- This says the charge will be $.45 + 2.00 which equals $2.45. That would be the charge to go one mile. What if the person wants to go further than that? I see C(m) but no "m" on the right side. Also, the phrase "plus a $2.00 minimum charge" leaves me wondering if all trips are charged an additional $2.00 or any trip no matter how short, must be charged at least $2.00. Did you copy the exact wording of the problem? I won't spend more time until I'm sure you are clear on exactly what the problems are asking.
 

dv8anly

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Joined
Feb 5, 2008
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Re: Functions

Hi, this is the exact wording for this problem it just asks me to write a linear function for this problem, and it only gives me two prices. In the next qustion is asks about a customer traveling more miles.
 
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