2.4 Solving Multi-Step Equations

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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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Lets try another!

• Ex d - 2 7
• 3
• (3) d - 2 7(3)
• 3
• d - 2 21
• 2 2
• d 23

• Complete the do-undo chart.
• DO UNDO
• -2 3
• 3 2
• To solve for d
• First multiply by 3.
• Then add 2.

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Heres 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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Lets 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 dont know what the first number is,
  lets call it n.
• The next number would be 1 more than n
• The next would be 2 more than n

n
n 1
n 2
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Lets 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