Question

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

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

Step2: Use the point - slope form

The point - slope form is \(y - y_1=m(x - x_1)\). Use \(m=-15\) and \((x_1,y_1)=(2,70)\).
\(y - 70=-15(x - 2)\)
\(y - 70=-15x + 30\)
\(y=-15x+100\)

Answer:

\(-15x + y = 100\)