© 2004  Rasmus ehf

Equations I

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Lesson 2.

You can use inverse operations to solve equations. If a term, that's a number or letter, is moved from one side of the equation to the other, the  sign in front of the term changes. Usually the unknown term is kept on the left hand side of the equation. 

Let's look at some different ways of solving equations.                                                     

Example 1      X - 3 = 10

X - 3 = 10	Move - 3 to the other side
	And X = 13

Example 2      X - 3 = 10

X - 3 = 10	Add +3 to both sides of the equation
	Then we get on the left side X and on the right side 13
	And we se that X = 13   Same result as in Example 1

You get the same result whether you move a number from one side of an equation to the other (remember to change the sign) or add the same number to both sides of the equation.   

Example 3      X + 3 = 10

X + 3 = 10	Move +3 to the other side
		You se that 10 - 3 = 7
		And X = 7

Example 4      X + 3 = 10

You get the same result whether you move a number from one side of an equation to the other (remember to change the sign) or add the same number to both sides of the equation.  

 Usually we move the unknown variables to the left hand side of the equation and the known values to the right. 

Example 5    2X - 7 = 8 - X 

The result is:  X = 5

Example 6     5X - 5 + 3X = 20 - 2X + 5

 You often need to take more than 1 step to solve an equation. 

5X - 5 + 3X = 20 - 2X + 5	1.    Collect like terms.
8X - 5 = 25 - 2X	2.    Move numbers to the right side of the equation and unknown values to the left.
8X + 2X = 25 + 5	3.    Collect like terms again.
10X = 30	4.    Divide each side by 10.
	5.    The result is:  X = 3

Practice these methods and then take Quiz 2 on Equations. 
Remember to use the checklist to keep track of your work.