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Algebra / Linear functions Difficulty: Hard

The cost of renting a carpet cleaner is $52 for the first day and $26 for each additional day. Which of the following functions gives the cost Cd, in dollars, of renting the carpet cleaner for d days, where d is a positive integer?

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Explanation

Choice A is correct. It's given that the cost of renting a carpet cleaner is $52 for the first day and $26 for each additional day. Therefore, the cost Cd, in dollars, of renting the carpet cleaner for d days is the sum of the cost for the first day, $52, and the cost for the additional d - 1 days, $26d-1. It follows that Cd=52+26d-1, which is equivalent to Cd=52+26d-26, or Cd=26d+26.

Choice B is incorrect. This function gives the cost of renting a carpet cleaner for d days if the cost is $78, not $52, for the first day and $26 for each additional day.

Choice C is incorrect. This function gives the cost of renting a carpet cleaner for d days if the cost is $26, not $52, for the first day and $52, not $26, for each additional day.

Choice D is incorrect. This function gives the cost of renting a carpet cleaner for d days if the cost is $130, not $52, for the first day and $52, not $26, for each additional day.