Algebra 1 Warm-up Solve these equations for x.

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Algebra 1 Warm-up Solve these equations for x.

• 1. 3x 12 7x
• 18 7x x
• x 13 4x 1
• 4x 10 6x - 8
• 8x 9 53 - 3x

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Warm up Answers

• x 3
• x -3
• x 4
• x 9
• x 4

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Lesson 3.3 Solving formulas for a Variable
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Key Vocabulary

• Order of Operations
• PEMDAS
• Formula (Formulae or Formulas)
• a mathematical relationship or rule expressed in
  symbols

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Do you remember

• When you solved equations you used the reverse
  Order of Operations?
• You will now use that skill to solve for a
  variable in a Formula!

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When solving for a variable, you must isolate the
variable. Think about opposites How do you
undo addition? Subtraction? Multiplication?
Division?
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Steps to Isolating the Variable Easy as 1 - 2 - 3

• Divide any parentheses out, unless solving for a
  variable in the parenthesis.
• Take care of all the addition and subtraction
  signs next.
• Then remove all of the division or multiplication
  pieces.

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Example 1 y mx b, Solve for m.

• y m x b

y b m x b - b
Subtract b from both sides.
y b m x x x
Divide by x on both sides.
Solve for m.
m y - b x
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Example 2 V lwh, Solve for h.

• V lwh

Divide by lw on both sides.
V lwh lw lw
Make sure h is by itself.
h V lw
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Example 3 P 2L 2W, Solve for L.
Solve for L.

• P 2L 2w

Subtract 2w from both sides.
P -2w 2L 2w -2w
P 2w 2L 2 2
Divide by 2 on both sides.
Make sure L is by itself.
L P-2w 2
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Summary Why is it important to be able to solve
for a specific variable within a formula?
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• Class work
• You try these
• Vf Vi at, Solve for t.
• A ½h (b1 b2), Solve for h.
• F 9/5 C 32, Solve for C.

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• Group Work
• Now that you have had some practice, get in
  groups of 3 or 4 and come up with three of your
  own variable equations. Specify which variable
  to solve for, and leave it at your groups table.
  
• Once all of the groups are done we will rotate
  until all of the groups have solved all other
  groups equations!

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Homework Worksheet 3.3