Note:

• A quadratic equation is a polynomial equation of degree 2.

• The ''U'' shaped graph of a quadratic is called a parabola.

• A quadratic equation has two solutions. Either two distinct real solutions, one double real solution or two imaginary solutions.

• There are several methods you can use to solve a quadratic equation:

1. Factoring
2. Completing the Square
4. Graphing

Solve for x in the following equation.

Example 4:

The equation is already set to zero.

Simplify the equation.

Method 1:Factoring

The equation is not easily factored. Therefore, we will not use this method.

Method 2:Completing the square

Add to both sides of the equation .

Divide both sides of the equation by and simplify.

Add to both sides of the equation:

Factor the left side and simplify the right side:

Take the square root of both sides of the equation:

Subtract from both sides of the equation:

In the equation ,a is the coefficient of the term, b is the coefficient of the x term, and c is the constant. Substitute for a, for b, and for c in the quadratic formula and simplify.

Method 4:Graphing

Graph the left side of the equation, Graph is nothing more than the x-axis. So what you will be looking for is where the graph of crosses the x-axis. Another way of saying this is that the x-intercepts are the solutions to this equation.

You can see from the graph that there are two x-intercepts, one at 2.7616977 and one at -3.710381013.

The answers are 2.7616977 and -3.710381013. These answers may or may not be solutions to the original equations. You must verify that these answers are solutions.

Check these answers in the original equation.

Check the solution x=2.7616977 by substituting 2.7616977 in the original equation for x. If the left side of the equation equals the right side of the equation after the substitution, you have found the correct answer.

• Left Side:

• Right Side:

Since the left side of the original equation is equal to the right side of the original equation after we substitute the value 2.7616977 for x, then x=2.7616977 is a solution.

Check the solution x=-3.710381013 by substituting -3.710381013 in the original equation for x. If the left side of the equation equals the right side of the equation after the substitution, you have found the correct answer.

• Left Side:

• Right Side:

Since the left side of the original equation is equal to the right side of the original equation after we substitute the value -3.710381013 for x, then x=-3.710381013 is a solution.

If you would like to test yourself by working some problems similar to this example, click on Problem

[Algebra] [Trigonometry]
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Author: Nancy Marcus