standard_description: Use similar triangles to explain why the slope m is the same between any two distinct points on a non-vertical line in the coordinate plane; derive the equation y = mx for a line through the origin and the equation y = mx + b for a line intercepting the vertical axis at b.
problem_activity: Narrative
This warm-up prompts students to carefully analyze and compare features of four equations. In making comparisons, students have a reason to use language precisely (MP6). The activity also enables the teacher to hear the terminologies students know and how they talk about characteristics of equations.
Launch
Groups of 2
Display image.
“Pick one that doesn’t belong. Be ready to share why it doesn’t belong.”
1 minute: quiet think time
Activity
“Discuss your thinking with your partner.”
2-3 minutes: partner discussion
Share and record responses.
Student Facing
Which one doesn’t belong?
A
\(3 + 3 = 6\)
B
\(6 = 4 + 2\)
C
\(4 + 3 = 7\)
D
\(\color{#3a53a4}{4 + 2 = 6}\)
Student Response
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Activity Synthesis
Display
\(6 = 4 + 2\)
and
\(4 + 2 = 6\)
.
“What is the same about these equations? What is different?” (They have the same numbers. The numbers are in a different order. One is blue and one is black. They both show that 4 plus 2 is 6.)


aligns: no