 # OTCQ Solve X = -4 3. Aim 3-4/3-5: How do we solve equations by working backwards? How do we reverse PEMDAS? Standards AA6 Analyze and solve verbal problems.

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OTCQ Solve X = -4 3

Aim 3-4/3-5: How do we solve equations by working backwards? How do we reverse PEMDAS? Standards AA6 Analyze and solve verbal problems whose solution requires solving a linear equation in one variable or linear inequality in one variable.

To solve two-step equations, undo the operations by working PEMDAS backwards in most cases. Example: Ask yourself, 1.What is the first thing we are doing to x? 2.What is the second thing? Recall the order of operations as you answer these questions. Dividing by 2 Subtracting 3 To undo these steps, do the opposite operations in opposite PEMDAS order.

1.Draw “the river” 2.Add 3 to both sides 3.Simplify 4.Clear the fraction - Multiply both sides by 2 5.Simplify 6.Check your answer Use a DO-UNDO chart as a shortcut to answering the questions. In the table, write the opposite operations in the opposite order DO UNDO (PEMDAS) ( Reverse PEMDAS ) ÷2 -3 Follow the steps in the ‘undo’ column to isolate the variable. + 3 + 3 = - 4 x = -8 -4 – 3 = -7 +3 · 2 2 · · 2

1) Solve 2x - 1 = -3 1.Draw “the river” 2.Add 1 to both sides 3.Simplify 4.Divide both sides by 2 5.Simplify 6.Check your answer + 1 + 1 2x = -2 2 2 x = -1 2(-1) - 1 = -3 -2 – 1 = -3 D U · 2 - 1 + 1 ÷ 2

+ 4 + 4 3 · · 3 x = 36 12 – 4 = 8 2) Solve 1.Draw “the river” 2.Add 4 to both sides 3.Simplify 4.Clear the fraction - Multiply both sides by 3 5.Simplify 6.Check your answer D U ÷ 3 - 4 + 4 · 3

3) Solve 3y – 1 = 8 1.y = 3 2.y = -3 3.y = 4.y =

3) Solve Exception to reverse Pemdas approach: If one side is a fraction/ratio then multiply both sides by the denominator first.

3) Solve D U - 4 ÷ 2 · 2 + 4 Because everything on the left is divided by 2. So we have to clear the fraction first.

3) Solve d – 4 = 6 + 4 + 4 d = 10 1.Draw “the river” 2.Clear the fraction - Multiply both sides by 2 3.Simplify 4.Add 4 to both sides 5.Simplify 6.Check your answer D U - 4 ÷ 2 · 2 + 4

4) Solve 1.d = -7 2.d = -19 3.d = -17 4.d = 17

5) Solve -3 -3 a = 35 1.Draw “the river” 2.Subtract 3 from both sides 3.Simplify 4.Clear the fraction – Multiply both sides by -7 5.Simplify 6.Check your answer D U ÷ -7 + 3 - 3 · -7 Do/Undo Chart – This one is tricky! Remember to always use the sign in front of the number.

6) Solve 5z + 16 = 51 1.z = -35 2.z = -7 3.z = 35 4.z = 7

- 1 - 1 5 · · 5 3x = 15 3 3 x = 5 7) Solve 1.Draw “the river” 2.Subtract 1 from both sides 3.Simplify 4.Clear the fraction - Multiply both sides by 5 5.Simplify 6.Divide both sides by 3 7.Simplify 8.Check your answer D U · 3 ÷ 5 + 1 - 1 · 5 ÷ 3

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