What is the quadratic formula? Do Now: Solve by completing the square x 2 +8x+15=0 I know the quadratic formula, do you?

Is there some way we can get the same result without all of the work? Yes, but to get our general formula, we are going to have to complete the square one more time. This time, we are going to complete the square using the standard form of the quadratic equation. This will give us a general solution for x

Here we go… Write in standard form Get the x’s alone on one side Divide by a.

The hard part… Take half of “b” and square it, add this number to both sides. Factor the left, and add the right

Almost done… Take the square root of both sides Solve for x

Final form? This is known as the QUADRATIC FORMULA. Instead of going through the process of completing the square we can just use this formula.

How do we use the quadratic formula? First we have to make sure our equation is written in STANDARD FORM. If the order is wrong you could get confused. Plug the coefficients in the correct locations

Example 2x 2 -3x-2=0 a=2, b=-3, c=-2

One more for me

Try on your own…

Review We got the quadratic formula by completing the square We need to remember to have the equation in standard form

Summary/HW Of the methods we have learned, which do you prefer and why? HW pg 81, 1-15 odd