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Grade 11 Precalculus · Lesson 2.2

Graphs of Functions

Read the equation, recognize the family, build the graph, and decide whether a relation is a function. One visual journey through power, piecewise, absolute-value, greatest-integer, and vertical-line ideas.
9 learning scenesInteractiveSame lesson material
Explanation
01

Recognize before you sketch

Graphing Toolkit · Start from the Family

Start by reconnecting equations with familiar graph shapes. Before plotting many points, identify the family and the information that controls its shape.

Explanationy=2x−1y=2x-1

Linear · slope 2 · y-intercept −1

Explanationy=x2y=x^2

Quadratic · vertex (0,0)

Explanationy=(x−2)2+3y=(x-2)^2+3

Quadratic · vertex (2,3)

Explanationy=x2−4x+3y=x^2-4x+3

Quadratic · standard form; find key points

Explanationy=∣x−2∣+3y=|x-2|+3

Absolute value · V-shape · vertex (2,3)

Worked example · translated quadratic
Sketch y=(x+1)2−4y=(x+1)^2-4.

Analyze first; the example is not complete until the graph is drawn.

Your turn · Recognize the family

Work this step on paper first. The solution stays hidden until you confirm you are ready.

Interactive lab

Verify · Translated Quadratic

After sketching by hand, compare your vertex, axis, intercepts, and shape with the exact graph.
-6-3.5-11.54-6-2.514.58 xy

Exact mathematical models; sampled curves use independent x/y scales. Toggle an equation to show or hide it.

Optional Desmos exploration

The native graph and checks work without this external service.

Where is the translated parabola’s vertex?

Your turn

What is the first feature to read from y=∣x−4∣+1y=|x-4|+1?
Explanation
02

Compare shapes

Power Functions · Even, Odd, and the Effect of n

Interactive lab

Power Function Explorer

Compare even and odd powers. Use the graph and the value at x = −1 to identify its symmetry.
Graph of y = x to power 2; equal axis units-4-4-3-3-2-2-1-111223344xy0

Rule: y = x2. Landmarks: (−1, 1), (0, 0), (1, 1).

Which symmetry does this power have?

As n increases, the graph becomes flatter near zero and steeper when |x| > 1. Both axes use the same unit length.

Interactive lab

Desmos · Power Family Comparison

Turn expressions on and off to compare even and odd powers on the same axes.
-2.2-1.101.12.2-5-1.751.54.758 xy

Exact mathematical models; sampled curves use independent x/y scales. Toggle an equation to show or hide it.

Optional Desmos exploration

The native graph and checks work without this external service.

Which symmetry statement is correct?
Key takeaway
Key pattern: even powers have the same general U-shaped behavior as a parabola; odd powers have the same general S-shaped behavior as a cubic. As the exponent increases, the graph becomes flatter near zero and steeper once ∣x∣>1|x|>1.
Worked example · classify before graphing
Compare the general shapes of f(x)=x6f(x)=x^6 and g(x)=x5g(x)=x^5.

Use parity, not a table of dozens of points.

Your turn · x⁶

Work this step on paper first. The solution stays hidden until you confirm you are ready.

Your turn

Question 1 of 2
Which statement is true for y=x7y=x^7?
Explanation
03

One function · different rules

Piecewise Functions · Choose the Interval First

Interactive lab

Piecewise endpoint decisions

Decide the interval first, then use its rule. At a boundary, ≤ or ≥ owns the closed point; < or > gives an open point.
f(x)={−x,x≤09−x2,0<x≤3x−3,x>3f(x)=\begin{cases}-x,&x\le0\\9-x^2,&0<x\le3\\x-3,&x>3\end{cases}

Compare the boundary with its neighbors: −0.5, 0, 0.5 and 2.5, 3, 3.5.

Which rule owns x = 0?
Worked example · three pieces
Graph f(x)={−x,x≤09−x2,0<x≤3x−3,x>3f(x)=\begin{cases}-x,&x\le0\\9-x^2,&0<x\le3\\x-3,&x>3\end{cases}.

For each rule: identify its interval, graph only that part, then mark its endpoint correctly.

Your turn · Piece 1

Work this step on paper first. The solution stays hidden until you confirm you are ready.

Final graph

Completed graph · three pieces

-4-20246-50510xy
Worked example · absolute value and root pieces
Graph f(x)={1−∣x−1∣,x≤2x−2,x>2f(x)=\begin{cases}1-|x-1|,&x\le2\\\sqrt{x-2},&x>2\end{cases}.

Do not graph the whole parent function; restrict each rule to its stated interval.

Your turn · First rule

Work this step on paper first. The solution stays hidden until you confirm you are ready.

Final graph

Completed graph · absolute value and root pieces

-4-202468-4-2024xy
Common mistake
Common mistake
Drawing each formula for all real x instead of clipping it to its interval.

Your turn

At x=3x=3, which condition owns the point: 0<x≤30<x\le3 or x>3x>3?
Explanation
04

Find the breaking point

Absolute Value → Piecewise

The central routine is to find where the expression inside the absolute value changes sign. Solve the inside equal to zero, split the number line there, then remove the absolute value with the correct sign.

∣u∣={u,u≥0−u,u<0|u|=\begin{cases}u,&u\ge0\\-u,&u<0\end{cases}
Understanding example · |x|
Rewrite f(x)=∣x∣f(x)=|x| as a piecewise function.

Try each checkpoint, or reveal all worked steps whenever you need them.

Your turn · For x≥0

Work this step on paper first. The solution stays hidden until you confirm you are ready.

Final graph

Completed graph · f(x)=|x|

-4-2024-4-202468xy
Worked example · shifted absolute value
Rewrite f(x)=∣x−3∣f(x)=|x-3| as piecewise.

Try each checkpoint, or reveal all worked steps whenever you need them.

Your turn · Breaking point

Work this step on paper first. The solution stays hidden until you confirm you are ready.

Final graph

Completed graph · f(x)=|x−3|

-2024680246xy
Worked example · reversed inside
Rewrite f(x)=∣1−x∣f(x)=|1-x| as piecewise.

Try each checkpoint, or reveal all worked steps whenever you need them.

Your turn · Breaking point

Work this step on paper first. The solution stays hidden until you confirm you are ready.

Final graph

Completed graph · f(x)=|1−x|

-4-202460246xy
Practice

Practice

∣2x−1∣|2x-1|

Find all breaking point(s), make sign intervals, then write the piecewise rule.

Practice

Practice

∣2−x∣|2-x|

Find all breaking point(s), make sign intervals, then write the piecewise rule.

Practice

Challenge

∣2−x∣+1|2-x|+1

Find all breaking point(s), make sign intervals, then write the piecewise rule.

Practice

Challenge

∣x2−1∣|x^2-1|

Find all breaking point(s), make sign intervals, then write the piecewise rule.

Advanced worked example
Rewrite f(x)=∣x2+x−6∣+2xf(x)=|x^2+x-6|+2x as a piecewise function.
x-axis: y = 0y-axis: x = 0-5-4-3-2-112345-55101520

    A quadratic inside absolute value can have more than one breaking point.

    Your turn · Factor inside

    Work this step on paper first. The solution stays hidden until you confirm you are ready.

    Your turn

    What is the first algebraic step for ∣3x+6∣|3x+6|?
    Explanation
    05

    Reverse the process

    Graph → Equation

    When a graph is given, identify the family first. For an absolute-value graph, read the vertex and use another point to determine the vertical scale.

    y=a∣x−h∣+ky=a|x-h|+k

    Vertex (h,k)(h,k) → substitute one more point → solve for aa.

    x-axis: y = 0y-axis: x = 0-112345678924681012(4, 1)(6, 5)
    • Given graph
    Worked example · equation from a V-graph
    An absolute-value graph has vertex (4,1)(4,1) and passes through (6,5)(6,5). Find its equation.

    Try each checkpoint, or reveal all worked steps whenever you need them.

    Your turn · Start with vertex form

    Work this step on paper first. The solution stays hidden until you confirm you are ready.

    Your turn

    A V-graph has vertex (−2,3)(-2,3). Which skeleton is correct?
    Given question graphIllustrative V-graph with the given vertex; steepness is not specified. Open circles exclude endpoints; filled circles include points. x horizontal axis; y vertical axis.-6-4-202012345678(−2, 3)xy
    Illustrative V-graph with the given vertex; steepness is not specified.
    Explanation
    06

    Step by step

    Greatest Integer Functions

    Interactive lab

    Greatest Integer Step Explorer

    Predict the greatest integer less than or equal to x. For negative inputs, move down the number line—not toward zero.
    Greatest integer graph; each step includes its left endpoint and excludes its right endpoint-4-4-3-3-2-2-1-111223344xy0● included endpoint · ○ excluded endpoint

    The output k satisfies k ≤ x < k + 1. At an integer, the output is that integer itself.

    Key takeaway

    Mr. Azzam’s graphing routine

    1. Find the subinterval length from the coefficient of x.
    2. Start subintervals from the zeros/boundaries of the inside expression.
    3. Place equality on the correct endpoint according to the direction of the x coefficient.
    4. Substitute the included endpoint to find the constant value on each step.
    Worked example · translated floor function
    Sketch f(x)=⌊x+2⌋f(x)=\lfloor x+2\rfloor.

    Try each checkpoint, or reveal all worked steps whenever you need them.

    Your turn · Step length

    Work this step on paper first. The solution stays hidden until you confirm you are ready.

    Final graph

    Completed graph · floor(x+2)

    -4-2024-4-20246xy
    Worked example · wider steps
    Sketch f(x)=⌊x2+1⌋+1f(x)=\lfloor \frac{x}{2}+1\rfloor+1.

    Try each checkpoint, or reveal all worked steps whenever you need them.

    Your turn · Coefficient of x

    Work this step on paper first. The solution stays hidden until you confirm you are ready.

    Final graph

    Completed graph · wider steps

    -6-4-20246-20246xy
    Worked example · negative coefficient and restricted domain
    Sketch f(x)=⌊−2x−1⌋f(x)=\lfloor-2x-1\rfloor, x∈[−1,1)x\in[-1,1).

    Try each checkpoint, or reveal all worked steps whenever you need them.

    Your turn · Step length

    Work this step on paper first. The solution stays hidden until you confirm you are ready.

    Final graph

    Completed graph · negative coefficient on restricted domain

    -1.5-1-0.500.511.5-4-3-2-1012xy
    Key takeaway
    Domain is all real numbers unless restricted. For the basic greatest-integer function, the range is all integers and the graph is constant on each step interval.

    Your turn

    Question 1 of 2
    What is ⌊−0.7⌋\lfloor-0.7\rfloor?
    Explanation
    07

    A visual decision

    Vertical Line Test

    Interactive lab

    Vertical Line Test Lab

    Predict how many points share this x-value, then check. A single line with two intersections disproves being a function; one passing line cannot prove it.
    Vertical line x = 0.8 on y = x²/4 − 2; equal axis units-4-4-3-3-2-2-1-111223344xy0

    Solid: relation. Dashed: test line. Window only; parabolas continue beyond it. Circle radius 2.5. Equal axis units.

    y = x²/4 − 2

    A graph represents y as a function of x if and only if no vertical line intersects the graph more than once.

    Your turn

    A vertical line crosses a graph at two points. What can you conclude?
    Given question graphIllustrative graph matching the stated information Open circles exclude endpoints; filled circles include points. x horizontal axis; y vertical axis.-3-113-3-2-10123xy
    Illustrative graph matching the stated information
    Explanation
    08

    Algebra can decide too

    Does an Equation Define y as a Function of x?

    Solve for yy. The question is whether each allowed x produces exactly one y-value.

    Worked example · function
    Does y−x2=2y-x^2=2 define y as a function of x?

    Try each checkpoint, or reveal all worked steps whenever you need them.

    Your turn · Solve for y

    Work this step on paper first. The solution stays hidden until you confirm you are ready.

    Worked example · not a function
    Does y2+x2=4y^2+x^2=4 define y as a function of x?

    Try each checkpoint, or reveal all worked steps whenever you need them.

    Your turn · Isolate y²

    Work this step on paper first. The solution stays hidden until you confirm you are ready.

    Worked example · rational function
    Does x2y+y=1x^2y+y=1 define y as a function of x?

    Try each checkpoint, or reveal all worked steps whenever you need them.

    Your turn · Factor y

    Work this step on paper first. The solution stays hidden until you confirm you are ready.

    Worked example · absolute value of y
    Does 2x−∣y∣=02x-|y|=0 define y as a function of x?

    Try each checkpoint, or reveal all worked steps whenever you need them.

    Your turn · Isolate

    Work this step on paper first. The solution stays hidden until you confirm you are ready.

    Common mistake
    Common mistake
    Seeing a ± sign and ignoring that it represents two possible outputs. The function question is about the number of y-values for one x.

    Your turn

    Does 3x−y=53x-y=5 define y as a function of x?
    Key takeaway
    09

    Connect everything

    Exam Strategy · Analyze → Plot → Sketch → Verify

    Key takeaway1 · Analyze

    Identify the family, restrictions, breakpoints, vertex, or step width.

    Key takeaway2 · Plot & Sketch

    Plot the controlling points/endpoints, then complete the actual graph. A graphing question is not finished before the graph.

    Key takeaway3 · Verify

    Use key points, endpoints, restrictions and Desmos verification to check—not replace—your hand-built graph.

    Lesson Mastery Checkpoint

    Rate each skill. This is only the starting signal; your actual Practice and Assessment performance will update the plan.

    Graph families & power functions

    Piecewise graphs & endpoints

    Absolute value ↔ piecewise

    Graph → equation

    Greatest integer functions

    Vertical line test

    Equation → function or not

    Rate all skills to prepare your personalized practice path.

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