Question

question 1 - 17
there is a linear relationship between the percent of battery charge remaining, y, on a cell phone and the number of hours, x, the phone has been used since a full charge.
the table of values represents this relationship.

which equation represents this relationship?

• 15x + y = 100

15x + y = 100
x + 15y = 100
x - 15y = 100

Explanation:

Step1: Find the slope \(m\)

Use the slope formula \(m=\frac{y_2 - y_1}{x_2 - x_1}\). Let \((x_1,y_1)=(2,70)\) and \((x_2,y_2)=(4,40)\).
\(m=\frac{40 - 70}{4 - 2}=\frac{-30}{2}=-15\)

Step2: Use the point - slope form \(y - y_1=m(x - x_1)\)

Use the point \((x_1,y_1)=(2,70)\) and \(m=-15\).
\(y - 70=-15(x - 2)\)
Expand: \(y - 70=-15x + 30\)
Rearrange to get \( - 15x+y=100\)

Answer:

\(-15x + y = 100\)