Math 8: Unit 5 - Functions

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Questions and Answers

I need help understanding the concept of a function as a rule or interpreting the graph of a function as a set of ordered pairs.

False (B)

I can describe the qualitative features of a function from a graph most of the time.

True (A)

I can identify basic properties of a single function with guidance.

True (A)

I need help comparing properties of two functions represented in different ways.

<p>False (B)</p> Signup and view all the answers

I can identify linear equations in the form with guidance. I need help interpreting the equation as defining a linear function or providing examples of nonlinear functions.

<p>False (B)</p> Signup and view all the answers

I can accurately describe the qualitative features of a function from a graph and sketch a graph that matches a verbal description.

<p>True (A)</p> Signup and view all the answers

I can clearly explain the relationship between quantities and justify my reasoning.

<p>True (A)</p> Signup and view all the answers

Is input 'any person' and output 'the month the person was born in' a function?

<p>True (A)</p> Signup and view all the answers

Is (2, 3), (0, 1), (2, -4), (3, -1), (2,4) a function?

<p>False (B)</p> Signup and view all the answers

Is the 'Earnings of Manager B' graph a function?

<p>True (A)</p> Signup and view all the answers

Is the Day/Temperature graph a function?

<p>False (B)</p> Signup and view all the answers

Is the Input/Output Table on the left a function?

<p>False (B)</p> Signup and view all the answers

Is the equation $y = -2x + 5$ a function?

<p>True (A)</p> Signup and view all the answers

Is the equation $x = 4$ a function?

<p>False (B)</p> Signup and view all the answers

Which graph shows a nonlinear function and why?

<p>Graph with a curve going up and down (C)</p> Signup and view all the answers

Given the linear function $y = 3x - 5$, find y when x = 2

<p>-1</p> Signup and view all the answers

Given the linear function $y = 3x - 5$, find the output when the input is 3

<p>4</p> Signup and view all the answers

Given the linear function $y = 3x - 5$, find the value of the dependent variable when the independent variable is -4

<p>-17</p> Signup and view all the answers

How much does A Plus Plumbing cost for each hour of work?

<p>$60</p> Signup and view all the answers

What is the one-time fee for A Plus Plumbing?

<p>$80</p> Signup and view all the answers

How much does Quality Plumbing charge for each hour of work?

<p>$50</p> Signup and view all the answers

What is the one-time fee for Quality Plumbing?

<p>$150</p> Signup and view all the answers

Can A Plus Plumbing and Quality Plumbing ever charge the same total for the same amount of time?

<p>True (A)</p> Signup and view all the answers

I can identify linear relationships and basic components of a function (e.g., slope and y-intercept) with guidance.

<p>True (A)</p> Signup and view all the answers

I need help constructing a function or interpreting the rate of change and initial value in context.

<p>False (B)</p> Signup and view all the answers

I can identify basic features of a graph with guidance.

<p>True (A)</p> Signup and view all the answers

I need help describing the relationship between quantities or sketching a graph based on a verbal description.

<p>False (B)</p> Signup and view all the answers

I can construct a function to model a linear relationship and determine the rate of change and initial value from a description, table, or graph most of the time.

<p>True (A)</p> Signup and view all the answers

I can sketch a graph based on a verbal description but may make small errors.

<p>True (A)</p> Signup and view all the answers

I can accurately construct a function to model a linear relationship and determine the rate of change and initial value from various representations.

<p>True (A)</p> Signup and view all the answers

I can clearly interpret these values in context and explain my reasoning.

<p>True (A)</p> Signup and view all the answers

What is the slope of the line $y = -3/2x + 3$?

<p>-3/2</p> Signup and view all the answers

What is the y-intercept of the line $y = -3/2x + 3$?

<p>3</p> Signup and view all the answers

Is a linear function a straight line with only one output?

<p>True (A)</p> Signup and view all the answers

After how many weeks will the puppy weigh 33 pounds for the linear function $y = 3/2x + 3$?

<p>20 weeks</p> Signup and view all the answers

Write the slope of the first piece of the graph?

<p>4</p> Signup and view all the answers

Write the slope of the second piece of the graph?

<p>0</p> Signup and view all the answers

Write the y-intercept of the first piece of the graph?

<p>0</p> Signup and view all the answers

Write the y-intercept of the second piece of the graph?

<p>24</p> Signup and view all the answers

Write an equation for the first piece of the graph?

<p>y=4x</p> Signup and view all the answers

Write an equation for the second piece of the graph?

<p>y=24</p> Signup and view all the answers

What does the slope of the first line segment represent in context?

<p>I am saving $400 per month</p> Signup and view all the answers

What does the slope of the second line segment represent in context?

<p>I stop saving money</p> Signup and view all the answers

Flashcards

What is a Function?

A relationship where each input has only one output.

What is a Linear Function?

A function represented by straight line equation in which for each input there is only one output.

What is a Nonlinear Function?

A function that does not form a straight line when graphed, indicating the rate of change is not constant.

What is Slope?

The constant rate of change of a linear function. It measures how much the dependent variable changes for every unit change in the independent variable.

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What is a y-intercept?

The point where a line crosses the y-axis on a graph. It represents the value of the dependent variable when the independent variable is zero.

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Study Notes

  • This is Math 8 Formative Assessment 1 covering Unit 5 Functions and Volume.

Defining Functions

  • A function is a rule where each input has only one output.
  • Can be represented as graphs, tables, equations, or verbal descriptions.
  • To determine if a relationship is a function, check that each input (x-value) has only one output (y-value).
  • Vertical line test: if a vertical line intersects the graph at more than one point, it is not a function.

Evaluating Functions

  • Given a function, you can find the output (y) for any input (x) by substituting x into the equation.
  • For f(x) = 3x - 5:
    • If x = 2, then f(2) = 3(2) - 5 = 1.
    • If f(x) = 7, then 7 = 3x - 5, so x = 4.

Comparing Functions

  • Linear functions have a constant rate of change (slope) and can be written in the form y = mx + b.
  • The slope (m) represents the rate of change (change in y over change in x).
  • The y-intercept (b) represents the initial value or starting point (value of y when x = 0).

Modeling Relationships with Functions

  • Can model real-world relationships using functions.
  • For example, the cost of a plumbing service can be modeled as a linear function of time (hours).
  • Need to determine the rate of change (slope) and initial value (y-intercept) from the given information (table, graph, or description).

Graphing Functions: Andre's Distance

  • Andre's distance from the starting point as a function of time:
    • Ran forward 20 yards.
    • Then ran back 5 yards.
    • Stood there for 3 seconds.
    • Walked back to the starting point.
  • The graph should have the axes labeled (distance in yards vs. time in seconds) and key points identified.

Linear Functions and Piecewise Functions

  • Given a table of values, identify the linear function that relates the variables (e.g., weight of a puppy vs. age in weeks).
    • Find the slope and y-intercept from the table.
    • Write the equation in the form y = mx + b.
  • Interpret the slope and y-intercept:
    • Slope represents the rate of change (e.g., weight increase per week).
    • Y-intercept represents the initial value (e.g., weight at birth).
  • Determine the value after a number of weeks.

Piecewise Functions

  • A piecewise function consists of different linear pieces over different intervals.

Variables Explained

  • In a graph showing a relationship between two variables, identify the dependent and independent variables.
    • The dependent variable is the output and depends on the independent variable (input).
    • Create a story or real-world context for the relationship shown in the graph.
  • A table and a piecewise function:
    • The domain is the interval of x-values for each piece.
    • The slope is the rate of change for each piece.
    • The y-intercept is the value of y when x = 0.
  • Write the equation for each piece in the form y = mx + b.
  • Calculate the value of y at a specific x-value using the appropriate equation.
  • Write the piecewise function by specifying the equation and domain for each piece.
  • Contextualize the slope:
    • Relate the slope of each line segment to the story or real-world context.
    • Determine if each line represents saving or spending money.

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