Lesson: Solve two-step equations

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Lesson Objective

We will be able to solve two-step equations.

Lesson Plan

 
Do Now: (5 minutes)
1) -5 + -9

2) Solve for x:
3x = -48

3) Solve for x:
x + 17 = 21


Direct Instruction:(20 minutes)
Yesterday we learned how to solve one-step equations like these. 
x – 3 = 10
 
9x= 72
 
What math did you do to solve the first equation?
What math did you do to solve the second equation?
(Talk about inverse operations).
 
4x + 8 = 20
 
How is this equation like the ones that we solved yesterday?  How is it different?  Ask students to solve the above equation. Have them share with a partner what they did to solve the equation.  Students will share what they did to solve the equation.  As a class discuss the ways that students approached the problem.
As we move through this year, our equations are going to get more and more complicated. It is important that we get in the habit of showing our work now to make the work that we are going to do down the road easier.

Have students put the work to solve the problem in their notes.

4x + 8 = 20
     - 8     -8
        4x = 20
         4      4
          x = 5
 
Solving equations is just undoing the math that was already done to the variable. First we have to deal with the terms that don’t have variables, then we move on to the coefficients. The equal sign means the same as, so this equation is telling us that 20 is the same as 4x + 8. Since = means the same as, we have to remember that whatever we do to one side of the equation, we have to do to the other, otherwise our sides will no longer be the same.
 
To solve an equation:
1) Use inverse operations to get the variable by itself.
2) Start with the terms that do not have a variable, then move to terms with the variable.
 
Have students solve 20 = 4x + 8.
 
Did our value of x change when we switched expressions in the equation? Why do you think that?
  
Remind students that the answer does not always have to be a whole number.


Guide Practice:(10 minutes)
 
5x – 14 = 6
 
10 = 18 – 2x

 27 = 8x – 13
 
 -7x + 9 = 79

Independent Practice: (10 minutes)
Two-step equations work-out
 

Lesson Resources

two step equations work out   Assessment
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