Keystone Algebra: Functions and Data Questions and Answers

Question 1

Which of the following sets of ordered pairs represents a function?

Accepted Answer

{(-2, 2), (-1, 5), (0, 8), (1, 5), (2, 2)}

Answer

A function is a relation where each input (x-value) corresponds to exactly one output (y-value). In the correct set, each x-value is unique and paired with only one y-value. The other options show at least one x-value paired with multiple y-values, which violates the definition of a function.

Question 2

A plumber charges a flat fee of $50 for a service call, plus an additional $75 per hour of labor. This relationship is modeled by the function C(h) = 75h + 50, where C(h) is the total cost and h is the number of hours of labor. What do the slope and y-intercept represent in this context?

Accepted Answer

The slope is the hourly rate, and the y-intercept is the flat fee.

Answer

In the linear function C(h) = 75h + 50, which is in the form y = mx + b, the slope 'm' represents the rate of change, and the y-intercept 'b' represents the initial value. Here, the slope is 75, which is the cost per hour ($75 hourly rate). The y-intercept is 50, which is the initial cost before any hours are worked (the $50 flat fee).

Question 3

The table below shows some values for a function, f(x). Which of the following statements best describes this function?

| x | f(x) |
|---|---|
| -2| 4   |
| -1| 1   |
| 0 | 0   |
| 1 | 1   |
| 2 | 4   |

Accepted Answer

It is a nonlinear function because the rate of change is not constant.

Answer

A function is linear if the rate of change (slope) between any two points is constant. From x=-2 to x=-1, the change in f(x) is 1-4 = -3. From x=-1 to x=0, the change is 0-1 = -1. Since the rate of change is not constant, the function is nonlinear. The repetition of f(x) values does not disqualify it from being a function.

Question 4

What is the domain of the function f(x) = √(x - 3)?

Accepted Answer

x ≥ 3

Answer

The domain of a function is the set of all possible input values (x-values) for which the function is defined. The square root function is only defined for non-negative numbers. Therefore, the expression inside the square root, (x - 3), must be greater than or equal to zero. Solving the inequality x - 3 ≥ 0 gives x ≥ 3.

Question 5

A researcher is tracking the population of a certain species of bird. The population started at 80 and has been decreasing by 6 birds each year. Which function, P(t), correctly models the bird population after t years?

Accepted Answer

P(t) = 80 - 6t

Answer

The initial population is the starting value, which corresponds to the y-intercept in a linear model. The rate of change, or slope, is a decrease of 6 birds per year, so it should be represented as -6. The function should model the initial population of 80 and subtract 6 for each year (t) that passes. Therefore, the correct function is P(t) = 80 - 6t.

Keystone Test Practice Test

Keystone Test Practice Test

Keystone Algebra: Functions and Data Questions and Answers