Question 695302
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There is a fixed cost, call that *[tex \LARGE C_f], then there is a variable cost, call that *[tex \LARGE C_v] that is applied to each of some variable number of things, of which there are a count of *[tex \LARGE x].  Then the total cost is *[tex \LARGE C_T(x)\ =\ C_f\ +\ C_vx].  In your phone company example, *[tex \LARGE x] has to be one less than the total number of minutes because the first minute is covered by the fixed cost.  So in that case, if you want *[tex \LARGE x] to represent the total number of minutes, then your function would have to be *[tex \LARGE C_T(x)\ =\ C_f\ +\ C_v(x\ -\ 1)], or, in the case of the numbers you provided, *[tex \LARGE C_T(x)\ =\ 0.25\ +\ 0.07(x\ -\ 1)] if you want Total Cost, *[tex \LARGE C_T] to be expressed in dollars, or *[tex \LARGE C_T(x)\ =\ 25\ +\ 7(x\ -\ 1)] if it is acceptable to express total cost in cents.


John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
<font face="Math1" size="+2">Egw to Beta kai to Sigma</font>
My calculator said it, I believe it, that settles it
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