Question 316885
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Let *[tex \Large x] represent the number of minutes used.


Let *[tex \Large C_1] represent the cost function for the first company.


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ C_1(x)\ =\ 0.07x\ +\ 26]


Let *[tex \Large C_2] represent the cost function for the second company.


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ C_2(x)\ =\ 0.12x]


When will *[tex \Large C_1\ =\ C_2]?


After some number of minutes *[tex \Large x] that satisfies:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 0.12x\ =\ 0.07x\ +\ 26]


Just solve for *[tex \Large x]


John
*[tex \LARGE e^{i\pi} + 1 = 0]
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