Respuesta :
Given:
The monthly cost is 37 min is $13.21
70 min cost is $17.50
Find-:
The monthly cost for 45 minutes of calls
Explanation-:
The linear equation is:
[tex]\begin{gathered} y=mx+c \\ \end{gathered}[/tex]Where,
[tex]\begin{gathered} m=\text{ Slope} \\ \\ c=Y-\text{ Intercept} \end{gathered}[/tex]The formula of the slope is:
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]The point is:
[tex]\begin{gathered} (x_1,y_1)=(37,13.21) \\ \\ (x_2,y_2)=(70,17.50) \end{gathered}[/tex]So, the slope is:
[tex]\begin{gathered} m=\frac{y_2-y_1}{x_2-x_1} \\ \\ m=\frac{17.50-13.21}{70-37} \\ \\ m=\frac{4.29}{33} \\ \\ m=0.13 \end{gathered}[/tex]Slope is:
The general equation of a line:
[tex]\begin{gathered} y=mx+c \\ \\ y=0.13x+c \end{gathered}[/tex]The value of "c" is:
[tex]\begin{gathered} y=0.13x+c \\ \\ (x,y)=(37,13.21) \\ \\ 13.21=0.13(37)+c \\ \\ c=13.21-4.81 \\ \\ c=8.4 \end{gathered}[/tex]The equation is:
[tex]\begin{gathered} y=mx+c \\ \\ y=0.13x+8.4 \end{gathered}[/tex]Cost at 45 min. is:
[tex]\begin{gathered} x=45 \\ \\ y=0.13x+8.4 \\ \\ y=0.13(45)+8.4 \\ \\ y=5.85+8.4 \\ \\ y=14.25 \end{gathered}[/tex]The 45 min cost is $14.25
