SOLVING QUADRATIC EQUATIONS

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
  3. Quadratic Formula
  4. Graphing
• All methods start with setting the equation equal to zero.

Solve for x in the following equation.

Example 3:

The equation is already set to zero.

Method 1: Factoring

The equation can be written in the equivalent form of The only way that a product can equal zero is if one or both of the factors equal zero.

Both answers are 8. This means that 8 is a double zero or double solution.

Method 2: Completing the square

Subtract 64 from both sides of the equation.

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,

Add 8 to both sides of the equation.

Method 3: Quadratic Formula

The quadratic formula is

In the equation , a is the coefficient of the term, b is the coefficient of the x term, and c is the constant. Simply insert 1 for a, -16 for b, and 64 for c in the quadratic formula and simplify

.

Method 4: Graphing

Graph y= the left side of the equation or and graph y= the right side of the equation or y=0. The graph of y=0 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.

The only x-intercept is located at x=8. When the graph is tangent to the x-axis at x=8, it means that there is a double zero (or solution or x-intercept) at The answer is

Check these answer in the original equation.

Check the answer x=8 by substituting 8 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 8 for x, then x=8 is a solution.

The solution to the equation is 8.

If you would like to go work another example, click on Example

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

If you would like to go back to the equation table of contents, click on Contents.

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