1. An Opportunity for Practice
Solving Equations
An Opportunity for Practice

2. Introduction
Equations are one of the most important tools used in Algebra. Equations are mathematical statements where 2 expressions are separated by an equal sign (=).
ex. 4x - 7 = 8x - 5
Most equations contain at least one unknown value denoted by a variable. Variables are symbols, usually letters, used to represent an unknown value.
ex. In the above equation, the variable is x.

3. Types of Equations
We will study several different equations throughout our Algebra I and Algebra II classes.
1) Equations in 1 variable.
ex. 4x - 7 = 8x - 5
4) Linear equations in 2 variables
ex. y = 2x - 1
2) Proportions
ex.
5) Quadratic Equations
ex. x2 + 7x = -12
3) Fractional Equations
ex.
Do not try to solve these equations now! We’ll explore each topic individually.

4. Equations in 1 Variable Ex. 4x - 7 = 8x - 5 x = -½
Think about these equations like a balanced scale. Your job is to get the variable by itself without disrupting the balance of the scale. The way to do this is use INVERSE (OPPOSITE) OPERATIONS.
1) We need to get the variable on 1 side. We have +8x on the right side. The opposite of positive is negative. Therefore, we’ll subtract 8x from each side.
4x - 7 = 8x - 5
-8x x
-4x - 7 = -5
2) To eliminate -7, we need to add 7 to each side.
3) Remember: -4x means “-4 times x”. The opposite of multiplication is division. We are going to divide both sides by –4.
-4x = 2
x = -½
Don’t forget to reduce your final answer!

5. Practice– Equations in 1 Variable
Solve each of the following equations using inverse operations. Be sure the equations stay balanced– if you do an operation on one side of the equal sign, you must do it on the other!
Once you’ve solved each equation, click the mouse again to check the solutions!
**Be careful with # 4– simplify the left side first!

6. Proportions
A proportion is an equation that sets two ratios (fractions) equal to each other.
The key to solving proportions is to rewrite it as an equation in 1 variable. We do this using a process called cross multiplying.
1) To cross multiply, multiply the top (numerator) of one fraction by the bottom (denominator) of the other.
2) Take the solutions and set them equal to each other.
3) Using inverse operations, solve the equation.

7. Practice-- Proportions
Solve each of the following proportions by cross multiplying.
After solving each of the proportions, click your mouse again to see the solutions.

8. Fractional Equations
Fractional equations are exactly what the name implies– equations that contain fractions.
Fractions can be a difficult concept, especially when working with equations. Our goal is to eliminate the fractions from the equation.
1) To eliminate the fractions we have to find a common denominator– the number that can be divided evenly by all the denominators in the equation. (In this case, the denominators are 3 and 5!)
** The smallest number that can be divided by 3 and 5 is A quick way to find a common denominator is to multiply your denominators!
2) Multiply every term on both sides of the equation by the common denominator. Simplify each term.
3) Solve the Equation in 1 Variable.

9. Practice– Fractional Equations
Solve each of the following equations by finding the common denominator.
Once you have solved the equations, click your mouse again to see the solutions.

10. Linear Equations in 2 Variables
Equations that contain 2 different variables are called linear because their graph is a line.
Unlike equations with only 1 variable, linear equations have an infinite number of solutions represented by ordered pairs (x,y). It is impossible to list all of them. Therefore, we represent the solution to linear equations by graphing.
Slope = y-intercept = -1
The easiest way to graph linear equations is to be sure the equation is in “y form”. Then, identify the slope and y-intercept*.
Each point on the line can be represented by an ordered pair with an x and y value. Every point on that line satisfies (makes the statement true) our equation.
*For more information on slope, y intercept, and graphing, click on this link: Slope of a Line.ppt

11. Practice– Linear Equations
Identify the slope and y-intercept for each of the following equations. Then draw the graph to represent all of the solutions. Be sure the equation is in y-form first!
After you graph each of the equations, click your mouse again to see the graph. Note the color of the line matches the color of the equation!
1) Slope = y-int = 5
2) Slope = ½ y-int = 0
3) Slope = y-int = 2

12. Quadratic Equations—Method 1
x2 + 7x = -12
Quadratic Equations are distinguished from other equations because they contain an “x2” term.
There are 2 methods to solve quadratic equations. Both methods require the same initial step: THE EQUATION MUST EQUAL 0! We call this “standard form”.
To write the above equation in standard form, add 12 to each side.
x2 + 7x + 12 = 0
ZERO PRODUCT PROPERTY
1) Factor the polynomial**.
(x + 3)(x + 4) = 0
2) Set factors = 0.
x + 3 = x + 4 = 0
x = x = -4
3) Solve the equations.
**For factoring practice click this link: Factoring Expressions.ppt

13. Quadratic Equations– Method 2
Not all quadratic equations can be solved using zero product property because not all expressions can be factored.
QUADRATIC FORMULA
x2 + 7x + 12 = 0
a = b = c = 12
x = -3 or -4
The key to quadratic formula is identifying a, b, and c. Then, plug the values into the formula!

14. Practice– Quadratic Equations
Solve each of the following quadratic equations using your method of choice.
After solving, click your mouse again to check your solutions.

15. Summary 1 Variable Proportions Fractional Linear equations
Unique variable
Use inverse operations
“keep the scale balanced”
Proportions
2 fractions equal
Cross multiply
Fractional
Contain at least 1 fraction
Multiply all terms by common denominator
Linear equations
Contain x and y
Infinite number of solutions represented as ordered pairs
Must be in y-form
Graph solution (line)
Quadratic equations
Contain x2
2 methods to solve: zero product property or quadratic formula
Must be in standard form (= 0)

16. Click your mouse again to check your solutions!
Mixed Practice
We have seen many different types of equations. See if you can determine which type of equation is listed below, then solve the equation!
Click your mouse again to check your solutions!