Quadratic Formula

This Movie (Quicktime)
will show you how to solve a quadratic equation using the quadratic formula.

The following is the movie transcript.

Hi my name is Shelby and today I’m going to show you how to solve a quadratic equation by using the quadratic formula.  By using the quadratic formula, you can always find the solution for ax to the second power plus bx plus c equals zero.  The quadratic formula is simply x equals the opposite of b plus or minus the square root of b to the second power minus four times ac over two a. Note that in order for the formula to work you must have the quadratic equation equal zero.

The problem that we are going to solve today will be x to the second power plus three x equals four. Setting this equation equal to zero will give you x to the second plus three x minus four equals zero.

By substituting the numbers from the problem into the formula a will become one b will become three and c will become negative four giving us the problem x equals a negative three plus and minus the square root of three to the second power minus four times one time a negative four all over two times one.

By using the order of operations you will solve the problem which will be x equals a negative three plus and minus the square root of nine plus sixteen over two. X equals a negative three plus and minus the square root of twenty five over two, leaving us to take the square root of twenty five.

By plus and minus being between the negative three and the five you must add and subtract the problem, giving you negative three minus five over two equals a negative eight over 2 leaving your first answer a negative four. The next one will be a negative three plus five over two equals two over two leaving you last answer a one.

This concludes how to solve a quadratic equation by using the quadratic formula.

End Movie Transcript

Posted at 06:20PM Dec 10, 2006 by llinebarger in Intermediate Algebra  |