OG详解-OG7 数学1 Q46

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 C(d), 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, $26(d-1). It follows that C(d) = 52+26(d-1), which is equivalent to C(d) = 52+26d-26, or C(d) = 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.