In this Warm-up, students determine how to rearrange an original equation into three different equivalent equations. The purpose is to remind students of moves allowed when rearranging equations. Students reason abstractly and quantitatively (MP2) when explaining why the equations are equivalent. This will be helpful in this lesson when students rearrange other linear equations and in the associated Algebra 1 lesson when students rearrange quadratic equations.

The purpose of the discussion is to recall some of the moves for rearranging equations to create new equations. Select students to share their reasoning for why the equations are equivalent. Here are some additional questions for discussion:

• “What are some other equivalent equations we could get by rearranging this one? Explain how you know they are equivalent to the original equation.” ( since it is the first solution with the constant terms combined, and that solution is equivalent to the original equation. There are many other reasonable answers.)
• “Two of the equations given have 0 on one side of the equation. Why might it be useful to have an equation in this form?” (In this form, we can set the other side of the equation equal to , then graph it to find the solutions as the -coordinates of the -intercepts.)
• “Andre rearranges the equation to . Is this equation equivalent to the original? If not, find an equivalent equation that has a similar form. Then, explain why this form might be useful.” (It is equivalent to the original equation. This could be useful for solving the equation for . After this, dividing both sides of the equation by 7 would solve for .)

In this activity, students examine work for common mistakes when solving equations. In the associated Algebra 1 lesson, students solve quadratic equations and must be mindful of possible mistakes in their work. Students construct viable arguments and critique the reasoning of others (MP3) when they identify the errors and explain their reasons to agree or disagree.