few_shots: 
Example 1:
Problem/activity:
Task
Materials
One 10-frame per pair of students (see example below)
[IMG]
Counters, 10 per pair of students
Decks of number cards 0-5 (with 4 of each number) or two 0-5 dice
Setup
This activity is done in pairs. The students sit side by side with 10-frame and deck of cards or dice. If they have cards, the cards are shuffled and placed face down in front of them.
Action
Player 1 flips a card or rolls the die. They place that many counters on the 10-frame. Player 2 flips a card or rolls the die. They place that many more counters on the 10-frame next to the counters already on the ten frame. The students count the total together.
A recording sheet can be added when the students have been introduced to equations and number sentences. For those students who can handle higher numbers, a deck of 0-10 cards and two 10-frames can be used.
This game can also be played alone.


Concept/skill: 
Solve addition and subtraction word problems, and add and subtract within 10, e.g., by using objects or drawings to represent the problem.

Answer: 
No. Though this task involves addition, it does not involve any word problems.

Example 2:
Problem/activity:
For each pair of numbers, determine if the values are equivalent. Explain your reasoning for each one.
a.
$$-0.25$$
and
$$\frac{1}{-4}$$
b.
$$-\left ( \frac{1}{4} \right )$$
and
$$\frac{-1}{-4}$$
c.
$$\frac{-1}{4}$$
and
$$-\frac{1}{4}$$


Concept/skill: 
Apply and extend previous understandings of multiplication to multiply a fraction or whole number by a fraction.

Answer: 
No. The expressions shown in this problem do not involve multiplying fractions with other fractions, nor whole numbers with fractions.

Example 3:
Problem/activity:
Find the general solution for:
$${\mathrm{cos}\left({\pi\over2}+x\right)=\mathrm{tan}{\pi\over4}}$$


Concept/skill: 
Prove the addition and subtraction formulas for sine, cosine, and tangent and use them to solve problems.

Answer: 
Yes. An initial step when solving for x in this problem requires the use of the addition formula for cosine on the left side of the equation.

Now, does the following problem or activity enable students to learn the full intent of the following concept or skill?

shot_info: im_task_001477_neg_0

K

fl_problem_001097_neg_0

7

fl_problem_001894_pos_0

HS_0
standard_description: Understand that a function is a rule that assigns to each input exactly one output. The graph of a function is the set of ordered pairs consisting of an input and the corresponding output. (Function notation is not required in Grade 8.)
problem_activity: Activity
This activity formally introduces students to the absolute value function as the function that takes an input value and gives its distance from the origin as the output. Students see two different ways to represent this function algebraically: using the absolute value notation and using the cases notation:
\(A(x)=|x|\)
\(A(x)=\begin{cases} x,& x \geq 0 \\ \text{-}x, & x < 0 \end{cases}\)
The equation in cases notation focuses on what has to happen algebraically to an input value to give its distance from the origin. Different rules apply to different intervals of the domain.
As students work, look for those who plot points for the graph of function
\(A\)
and those who sketch two lines. Ask students who sketch different types of graphs to share during discussion.
Launch
Arrange students in groups of 2. Give students a few minutes of quiet work time, than time to share their response with their partner. Follow with a whole-class discussion.
Writing, Listening, Conversing: MLR1 Stronger and Clearer Each Time.
Use this routine to help students improve their verbal and written responses to the last question. Give students time to meet with 2–3 partners to share and get feedback on their responses. The listener should press for detail and precision in language by asking “Can you give a few examples?”, “How do you know?”, or “Can you demonstrate your thinking using the graph?” Invite students to go back and revise or refine their written explanation based on the feedback from peers. This will help students understand different ways to represent an absolute value function.
Design Principle(s): Optimize output (for explanation); Cultivate conversation
Student Facing
The function
\(A\)
gives the distance of
\(x\)
from 0 on the number line.
Complete the table and sketch a graph of function
\(A\)
.
|       \(x\)       | \(A(x)\) |
|-------------------|----------|
|         8         |          |
|                   |   5.6    |
|      \(\pi\)      |          |
|    \(\frac12\)    |          |
|                   |    1     |
|         0         |          |
| \(\text-\frac12\) |          |
|        -1         |          |
|       -5.6        |          |
|                   |    8     |
[IMG]
Andre and Elena are trying to write a rule for this function.
Andre writes:
\(A(x)=\begin{cases} x,& x \geq 0 \\ \text-x, & x < 0 \\ \end{cases}\)
Elena writes:
\(A(x) = |x|\)
Explain why both equations correctly represent the function
\(A\)
.
Student Response
Teachers with a valid work email address can
click here to register or sign in
for free access to Student Response.
Anticipated Misconceptions
Students who interpret the “
\(\text-x\)
” in Andre's rule to mean "negative
\(x\)
" (rather than "the opposite of
\(x\)
") may be unsure how to use that information. Ask students to evaluate the function for specific values of
\(x\)
and to write down each step. For instance, when
\(x\)
is -2,
\(A(\text{-}2)\)
is
\(\text{-}(\text{-}2)\)
, which is 2.
Activity Synthesis
Select previously identified students to display their graph of function
\(A\)
. Ask students who plotted only the ordered pairs in the table whether the pairs that are not in the table, if plotted, would also fall on the same two lines. Emphasize that
\(A\)
can be shown with two lines.
Next, ask students to share their response to the last question. Students may find Elena's rule easier to explain because of their work with absolute value in recent activities and struggle to explain Andre's rule.
We can reason about Andre's equation a couple of ways:
By thinking about rules: The equation is that of a piecewise function because different rules are applied to different parts of the domain to give the "distance from 0" as the output:
When the input
\(x\)
is positive or 0, its distance from 0 is that same number,
\(x\)
.
When the input
\(x\)
is negative, its distance from 0 is the opposite of the number,
\(\text-x\)
.
By using the graph: The two halves of the graph are lines with different slopes.
If we cover up the left side of the vertical axis and see only positive values of
\(x\)
, we see a line with a slope of 1 and that represents
\(y=x\)
.
If we cover up the right side and see only negative values of
\(x\)
, we see a line with a slope of -1 and that represents
\(y=\text{-}x\)
Explain to students that:
Function
\(A\)
is the
absolute value function
. It gives the distance of an input value from a certain value, the origin, in this case.
The graph of function
\(A\)
is a V shape with the two lines of points converging at
\((0,0)\)
, which is the minimum of the graph. We call this point the
vertex
of the graph. It is the point where the graph changes direction.
The absolute value function is also a piecewise function because different rules are applied to different parts of the domain to get the output.
Representation: Develop Language and Symbols.
Create a display of important terms and vocabulary. Invite students to suggest language or diagrams to include that will support their understanding of: absolute value function, vertex, cases notation.
Supports accessibility for: Conceptual processing; Language


aligns: no