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An online clothes delivery service charges a flat fee for joining in addition to a monthly subscription cost. The graph shows the relationship between the number of months, , and the total cost, f(x).

An online clothes delivery service charges a flat fee for joining in addition to a-example-1
User Ghimire
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1 Answer

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To find the equation of the line shown, we need two points:


\begin{gathered} (x_1,y_1)=(0,100) \\ \text{and} \\ (x_2,y_2)=(20,200) \end{gathered}

The equation of the line goes by:


y-y_1=m(x-x_1)

The find m, the slope, we use the formula below and find m.


\begin{gathered} m=(y_2-y_1)/(x_2-x_1)_{} \\ m=(200-100)/(20-0) \\ m=(100)/(20) \\ m=5 \end{gathered}

Now, let's put the point and m to find the equation:


\begin{gathered} y-y_1=m(x-x_1) \\ y-100=5(x-0) \\ y-100=5(x) \\ y-100=5x \\ y=5x+100 \end{gathered}

Changing to functional notation, this will be:


f(x)=5x+100

2nd answer choice is correct.

User Andrew Cheong
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