Question

Mia opens a coffee shop in the first week of January. The function W(x) = 0.002x3 - 0.01x2 models the total number of customers visiting the shop since it opened after x days. She then opens an ice cream parlor in the month of February. The function R(x) = x2 - 4x + 13 models the total number of customers visiting the parlor since it opened after x days. 
Which function represents the difference, D(x), in the number of customers visiting the two shops?

D(x) = 0.002x3 + 1.01x2 - 4x + 13


D(x) = 0.002x3 + 0.99x2 + 4x - 13


D(x) = 0.002x3 - 1.01x2 + 4x - 13


D(x) = 0.002x3 - 0.99x2 - 4x + 13

Answer 1

Writing the two equations in full and subtracting R(x) from W(x) to arrive at D (x) gives the answer. This is shown below;

W(x) = 0.002x^3 - 0.01x^2 + 0x + 0
R (x) =        0x^3 +       x^2 - 4x +13 -
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D(x) = 0.002x^3 -1.01x^2 + 4x - 13