Question

diane is watching a movie on her laptop. as diane is watching the movie, the amount of battery charge on the laptop decreases. the table below shows the linear relationship between the time x (in hours) since the movie began and the amount of battery charge y (as a percentage).
time (hours) | 0 | 1 | 2 | 3
amount of battery charge (%) | 80 | 60 | 40 | 20
write a linear equation to represent the relationship between x and y.

Explanation:

Step1: Identify y-intercept (x=0)

When $x=0$, $y=80$, so $b=80$.

Step2: Calculate slope (rate of change)

Slope $m=\frac{y_2-y_1}{x_2-x_1}=\frac{60-80}{1-0}=-20$

Step3: Plug into linear form $y=mx+b$

Substitute $m=-20$ and $b=80$ into the slope-intercept equation.

Answer:

$y=-20x+80$