Express the price of one gallon of unleaded gasoline as a function of time for the period starting January 2004.
Define the variables and initial conditions.
Let \( P(x) \) represent the price per gallon of unleaded gasoline, where \( x \) is the number of months since January 2004. On January 1st, 2004 (\( x = 0 \)), the price is \( \$1.65 \). The price increases at a rate of 6 cents (\( \$0.06 \)) per month.
Formulate the function.
The price \( P(x) \) can be expressed as:
\[
P(x) = 1.65 + 0.06x
\]
The price of one gallon of unleaded gasoline as a function of time is:
\[
\boxed{P(x) = 1.65 + 0.06x}
\]
What was the price of 18 gallons of gas on May 1st, 2004?
Determine the number of months since January 2004.
May 1st, 2004 is 4 months after January 1st, 2004. Thus, \( x = 4 \).
Calculate the price per gallon on May 1st, 2004.
Using the function \( P(x) = 1.65 + 0.06x \), substitute \( x = 4 \):
\[
P(4) = 1.65 + 0.06(4) = 1.65 + 0.24 = 1.89
\]
Calculate the price of 18 gallons.
The price of 18 gallons is:
\[
18 \times 1.89 = 34.02
\]
The price of 18 gallons of gas on May 1st, 2004 is:
\[
\boxed{\$34.02}
\]
What was the price of 18 gallons of gas on September 1st, 2004?
Determine the number of months since January 2004.
September 1st, 2004 is 8 months after January 1st, 2004. Thus, \( x = 8 \).
Calculate the price per gallon on September 1st, 2004.
Using the function \( P(x) = 1.65 + 0.06x \), substitute \( x = 8 \):
\[
P(8) = 1.65 + 0.06(8) = 1.65 + 0.48 = 2.13
\]
Calculate the price of 18 gallons.
The price of 18 gallons is:
\[
18 \times 2.13 = 38.34
\]
The price of 18 gallons of gas on September 1st, 2004 is:
\[
\boxed{\$38.34}
\]
The price of one gallon of unleaded gasoline as a function of time is:
\[
\boxed{P(x) = 1.65 + 0.06x}
\]
The price of 18 gallons of gas on May 1st, 2004 is:
\[
\boxed{\$34.02}
\]
The price of 18 gallons of gas on September 1st, 2004 is:
\[
\boxed{\$38.34}
\]