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Published byDavid Rigley Modified over 2 years ago

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A Question of Balance The two sides on a balanced scale must be equal to each other What does the Egg weigh? E + 6 = 11 E = 5

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When you do something to one side of an equation, You have to do the same thing to the other side. A Question of Balance 2(3) + 410 The two sides of an equation are equal to each other The left side and the right side must be balanced

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A Question of Balance If the two sides of an equation are not equal… 3(7) – 2 20 + 1

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A Question of Balance If the two sides of an equation are not equal… 3(7) – 2 20 + 1 Then it is not balanced!

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A Question of Balance What happens if we change one of the sides of a balanced equation? Then it is not balanced! 8 + 3 11 + 1+ 1 8 + 3 + 1

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A Question of Balance What happens if we change one of the sides of a balanced equation? Then it is not balanced! 8 + 3 + 1 11 We need to make the same change to the other side! + 1

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We need to make the same change to the other side! What happens if we change one of the sides of a balanced equation? A Question of Balance 8 + 3 + 111 + 1 We need to make the same change to the other side! Whatever thou dost unto the left, thou also must do unto the right. The 11 th Commandment (for equations):

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To solve an equation means to find every number that makes the equation true. We do this by adding or subtracting to each side of the equation … but always keep it balanced!

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In the equation, 7 added to a number gives 15… Solving the equation means, finding the value of the variable that makes the equation true. Let’s go back to the balance

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x + 7 15 Whatever thou dost unto the left, thou also must do unto the right. The 11 th Commandment (for equations): - 7 Subtract 7 from both sides Simplify both sides

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Whatever thou dost unto the left, thou also must do unto the right. The 11 th Commandment (for equations): x 8 Subtract 7 from both sides Simplify both sides Now we know the value of x

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x 8 Subtract 7 from both sidesSimplify both sides Now we know the value of x Whatever thou dost unto the left, thou also must do unto the right. The 11 th Commandment (for equations): So the solution goes like this… x + 7 = 15 x + 7 – 7 = 15 – 7 x = 8

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In some equations, the solution is obvious. x – 7 = 12 x = 19 5n = 35 n = 7 20 + h = 41 h = 21 = 3 c = 24 We can simply work the operation backwards in our head to get the answer.

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But in other equations, the solution is not so obvious. We have to know what operation(s) must be done to solve it, and work it out carefully.

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You have to do the inverse operation to both sides to get the variable by itself The opposite of addition is subtraction The opposite of subtraction is addition The opposite of multiplying by is multiplying by The opposite of multiplication is division

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Multi-step equations When and equation has more than one operation you still have to isolate the variable by doing the following: Make sure variable terms are all on one side, and constant terms are on the other. Simplify Divide by the coefficient of the variable.

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3x + 5 12 How would we solve 3x + 5 = 12? Let’s take another look at the balance – 5 Subtract 5 from both sides

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3x 7 How would we solve 3x + 5 = 12? Let’s take another look at the balance Subtract 5 from both sides Simplify

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3x 7 How would we solve 3x + 5 = 12? Let’s take another look at the balance Subtract 5 from both sides Simplify 3 3 Divide both sides by coefficient of the variable (3)

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7 How would we solve 3x + 5 = 12? Let’s take another look at the balance Subtract 5 from both sides Simplify 3 x Divide both sides by coefficient of the variable (3) So the solution is:

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Let’s try some more equations Remember, we have to keep the equations balanced! Solve: 8m – 10 = 36 8m – 10 + 10 = 36 + 10 8m = 46 8 m =m = w = 84

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5x 2 = x + 4 Solve: 5x 2 + 2 = x + 4 + 2 Notice that there are variables on both sides 5x = x + 6 Get rid of the -2 on the left side Simplify 5x – x = x – x + 6 Get rid of the x on the right side 4x = 6 Get rid of the cofficient of x 4 x = Simplify

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