EquationsIts all about equivalence
An equation ….Is a mathematical sentence that says that two expressions are equal.What is on the left = what is on the right
There are two types of equations ….. Numerical5 + 9 = 14Algebraic2x – 3 = 14
Modeling of equations2x + 4 = -6
Model these in your notes:-3x + 4 = 2x5+ 2x = -1 6x – 3 = -2x + 4
Our goal with equations is to:Find the value of “x” or the variableSolve itTo do this we must rewrite the equation in progressively simpler equivalent forms of the original equation.
So to do this we need to use the most important rule for equations …..What you do to one side you MUST do to the other
2x + 4 = -6From the equation we can choose to try the following:+ 2x    -2x
2x + 4 = -6From the equation we can choose to try the following:+ 2x    -2x + 4     -4
2x + 4 = -6From the equation we can choose to try the following:+ 2x    -2x + 4     -4   -6    + 6
2x + 4 = -6From the equation we can choose to try the following:+ 2x    -2x + 4     -4   -6    + 6  x 2 or ÷2
2x + 4 = -6
+ 2x to both sides4x + 4 = 2x - 6
- 2x on both sides4=-2x-6
+ 4 on both sides2x + 8 = -2
-4 on both sides2x = -10
-6 on both sides2X – 2 = -12
+6 on both sides2x + 10 = 0
Multiply both sides by 24x + 8 = -12
Divide both sides by 2
Divide both sides by 2x + 2 = -3
None of these steps are WRONG … an equivalent equation results every timeBUTthe ONE operation that makes the equation simpler (shorter) is the one you are looking for!
For these, list all the possible things you could do to each side-3x + 4 = x5+ 2x = -1 5x – 3 = -2x + 4
-3x + 4 = x-3x   + 3x+ 4   -4+x   -xx -3   ÷ -3
5+ 2x = -1  + 5      -5+ 2x     -2x-1        +1x 2       ÷ 2
5x – 3 = -2x + 4+ 5x      -5x-3        +3-2x      +2x+ 4       -4x 5      ÷ 5x -2     ÷ -2
For the each of the 3 equations:Write out the equivalent form for each
Equivalent equations

Equivalent equations

  • 1.
  • 2.
    An equation ….Isa mathematical sentence that says that two expressions are equal.What is on the left = what is on the right
  • 3.
    There are twotypes of equations ….. Numerical5 + 9 = 14Algebraic2x – 3 = 14
  • 4.
  • 5.
    Model these inyour notes:-3x + 4 = 2x5+ 2x = -1 6x – 3 = -2x + 4
  • 6.
    Our goal withequations is to:Find the value of “x” or the variableSolve itTo do this we must rewrite the equation in progressively simpler equivalent forms of the original equation.
  • 7.
    So to dothis we need to use the most important rule for equations …..What you do to one side you MUST do to the other
  • 8.
    2x + 4= -6From the equation we can choose to try the following:+ 2x -2x
  • 9.
    2x + 4= -6From the equation we can choose to try the following:+ 2x -2x + 4 -4
  • 10.
    2x + 4= -6From the equation we can choose to try the following:+ 2x -2x + 4 -4 -6 + 6
  • 11.
    2x + 4= -6From the equation we can choose to try the following:+ 2x -2x + 4 -4 -6 + 6 x 2 or ÷2
  • 12.
    2x + 4= -6
  • 13.
    + 2x toboth sides4x + 4 = 2x - 6
  • 14.
    - 2x onboth sides4=-2x-6
  • 15.
    + 4 onboth sides2x + 8 = -2
  • 16.
    -4 on bothsides2x = -10
  • 17.
    -6 on bothsides2X – 2 = -12
  • 18.
    +6 on bothsides2x + 10 = 0
  • 19.
    Multiply both sidesby 24x + 8 = -12
  • 20.
  • 21.
    Divide both sidesby 2x + 2 = -3
  • 22.
    None of thesesteps are WRONG … an equivalent equation results every timeBUTthe ONE operation that makes the equation simpler (shorter) is the one you are looking for!
  • 23.
    For these, listall the possible things you could do to each side-3x + 4 = x5+ 2x = -1 5x – 3 = -2x + 4
  • 24.
    -3x + 4= x-3x + 3x+ 4 -4+x -xx -3 ÷ -3
  • 25.
    5+ 2x =-1 + 5 -5+ 2x -2x-1 +1x 2 ÷ 2
  • 26.
    5x – 3= -2x + 4+ 5x -5x-3 +3-2x +2x+ 4 -4x 5 ÷ 5x -2 ÷ -2
  • 27.
    For the eachof the 3 equations:Write out the equivalent form for each