Question

A phone company charges 15.99 a month and 9 cents for every minute above 130 minutes. Write an expression for the monthly phone charge, P, in dollars, as afunctionof the number of minutes, m, used that month.

Answer 1

Answer:

$p=\left \{ {{15.99,m[tex]\leq$130} \atop {15.99+0.09*(m-130),m>130}} \right.[/tex]

Step-by-step explanation:

We will have a partial funcion to define an expression for the monthly phone charge, because we have a condition that changes the monthly cost.

For months under 130 minutes, there will not be any additional charge other that tha base monthly cost, so the expression for the months under 130 minutes will be the monthly fee.

For months over 130 we will have the same information than above, but we have to add a fee for every minute over 130 minutes. To find the amaunt of minutes over 30 minutes we will just subtract 130 to the amount of minutes used: (m-130). Then we will multiply that number times the cos of each minute over 130 minutes: 9*(m-130). Finally we will add the basic phone fee: 15.99 + (0.09*(m-130)).

Now we set the conditions and use the correct notation for a partial function and we get:

$p=\left \{ {{15.99,m[tex]\leq$130} \atop {15.99+0.09*(m-130),m>130}} \right.[/tex]