Question

In this activity, you will create an equation for a function represented by a verbal description.

Vicky charged her phone’s battery to 100 percent. Then she took the phone off the charger. When her phone is off the charger, it loses 5 percent of its battery life every hour. What function models the percentage of battery life left in terms of the number of hours since Vicky took it off the charger?

What is the initial value of the function? Is it positive or negative? Explain your answer.

What is the function’s rate of change? Is it positive or negative? Explain your answer.

Answer 1

1) The initial value of the function is the y-value when the x-value is zero. The number of hours is the x-value and the percentage of battery life left is the y-value. When the number of hours, x, is 0, the percentage of remaining battery life, y, is 100 percent. So, the initial value of the function is 100. The initial value is positive because the percentage of remaining battery life cannot be negative.

2) The rate of change is the rate at which the y-value changes with respect to a change in the x-value. When off the charger, the phone loses its battery life at a constant rate of 5 percent per hour. So, the function’s rate of change is -5. The rate of change is negative because the rate indicates that the percentage of remaining battery life decreases as the number of hours increases.

Step-by-step explanation: I just did the tutorial right now i hope this helps

Answer 2

part a = The number of hours since Vicky took the phone off the charger is the independent quantity, so the variable x should represent it.

part b = The percentage of battery life left in hours is the dependent quantity, so the variable y should represent it.

part c = The initial value of the function is the y-value when the x-value is zero. The number of hours is the x-value and the percentage of battery life left is the y-value. When the number of hours, x, is 0, the percentage of remaining battery life, y, is 100 percent. So, the initial value of the function is 100. The initial value is positive because the percentage of remaining battery life cannot be negative.

part d = The rate of change is the rate at which the y-value changes with respect to a change in the x-value. When off the charger, the phone loses its battery life at a constant rate of 5 percent per hour. So, the function’s rate of change is -5. The rate of change is negative because the rate indicates that the percentage of remaining battery life decreases as the number of hours increases.

part e = The rate of change of the function, m, is -5, and the initial value of the function, b, is 100. Substitute the values of m and b in the equation y = mx + b. The equation of the function that models the phone’s remaining battery life in terms of the number of hours from the time Vicky took it off the charger is y = -5x + 100.

Explanation:

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