standard_description: Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so.
problem_activity: Activity
In this activity, students get a chance to practice solving equations with a single variable. The equations resemble the types of equations students see in the associated Algebra 1 lesson after they substitute for a variable. Students will work in pairs and each partner is responsible for answering the questions in either column A or column B. Although each row has two different problems, they share the same answer. Ensure that students work their problems out independently and collaborate with one another when they do not arrive to the same answers. Students construct viable arguments and critique the reasoning of others (MP3) when they resolve errors by critiquing their partner's work or explaining their reasoning.
Launch
Arrange students in groups of 2.
Student Facing
Solve each equation.
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Student Response
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Activity Synthesis
The purpose of the discussion is to recall strategies for solving equations with one variable. Select students to share their solutions including their reasoning for the steps they take.
Some questions for discussion:
"When there is a variable inside parentheses, how did you approach the problem?" (I distributed the value multiplying the parentheses to remove the parentheses then solved the equation as usual.)
"How could you check that your answer works using the original equation?" (I could substitute the value for
\(x\)
into the original equation and determine if the equation is true.)


aligns: no