Answer:
Given,
The original percentage of battery = 20 %,
Also, Every minute that passes, an additional 5%,
So, the increment in percentage after x minutes = 5x percentage
Thus, the final battery after x minutes = ( 20 + 5x ) %
Let y represents the total percentage of battery after x minutes,
⇒ y = 20 + 5x
Which is the required function that shows the given situation.
For graphing,
y = 20 + 5x is a line having x-intercept = (-4,0)
And, y-intercept = (0,20)
Also, battery's capacity and time can not be negative,
⇒ x ≥ 0 , y ≥ 0