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2.4 Solving Multi-Step Equations Indicators: PFA7, PFA8, PFA9 Written by ??? Edited by Eddie Judd, Crestwood Middle School Edited by Dave Wesley, Crestwood Middle School

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To Solve: Undo the operations by working backward. Ex: x + 9 = 6 5 Ask yourself: What is the first thing we are doing to x? The second thing? Recall the order of operations as you answer these questions. dividing by 5 adding 9 To undo these steps, do the opposite operations in opposite order.

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The DO-UNDO chart Use a chart as a shortcut to answering the questions. DO UNDO ÷5 -9 +9 ·5 Follow the steps in the ‘undo’ column to isolate the variable. Ex: x + 9 = 6 5 First subtract 9. x + 9 - 9 = 6 - 9 5 x = -3 5 Then multiply by 5. (5) x = -3(5) 5 x = -15

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Let’s try another! Complete the do-undo chart. DO UNDO -2 ·3 ÷ 3 +2 To solve for d: First multiply by 3. Then add 2. Ex: d - 2 = 7 3 (3) d - 2 = 7(3) 3 d - 2 = 21 +2 +2 d = 23

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Here’s a tricky one! Remember to always use the sign in front of the number. DO UNDO ÷ -7 - 3 +3 · -7 To solve for a: First subtract 3. Then multiply by -7. Ex: 3 - a = -2 7 3 - a = -2 7 -3 -3 - a = -5 7 (-7)(- a) = (-5)(-7) 7 a = 35

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Try a few on your own. 5z + 16 = 51 14n - 8 = 34 4b + 8 = 10 -2

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Example 1 5z + 16 = 51

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Example 2 14n - 8 = 34

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Example 3 4b + 8 = 10 -2

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The answers: DO UNDO · 5 - 16 +16 ÷ 5 z = 7 DO UNDO · 14 +8 -8 ÷ 14 n = 3 DO UNDO · 4 · -2 +8 - 8 ÷ -2 ÷ 4 b = -7

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Consecutive Numbers Consecutive means-- In order/In sequence. Ex: 1, 2, 3… 10,11,12… 20, 22, 24, 26… (Evens) 51, 53, 55 etc... (Odds)

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Let’s try one!!! Find three consecutive integers that have a sum of 15. What is this asking? + + = 15

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Almost there! + + = 15 Since we don’t know what the first number is, let’s call it “n.” The next number would be “1 more than n” The next would be “2 more than n” n n + 1n + 2

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Let’s complete the problem! So the problem looks like this: n + (n + 1) + (n + 2) = 15 Scary Right?!? Nah!!! 3n + 3 = 15 LIKE TERMS!!! EASY!!!

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Solve It!! 3n + 3 = 15 - 3 - 3 3n = 12 ___ 3 3 n = 4 So if n = 4, (n + 1) = 5 and (n + 2) = 6 Your three consecutive numbers are: 4, 5, and 6

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Assignment Algebra 1 Pg 95 Problems 11-26 all, 29 and 33-37 odds Honors Algebra 1 Pg 95 Problems 11-23 odd, 25-28 all, 31-37 all 40-42 all

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