Title: Solving Quadratic Equations by the Quadratic Formula
1Solving Quadratic Equations by the Quadratic
Formula
2THE QUADRATIC FORMULA
- When you solve using completing the square on
the general formula you get - This is the quadratic formula!
- Just identify a, b, and c then substitute into
the formula.
3WHY USE THE QUADRATIC FORMULA?
- The quadratic formula allows you to solve ANY
quadratic equation, even if you cannot factor it. - An important piece of the quadratic formula is
whats under the radical - b2 4ac
- This piece is called the discriminant.
-
4WHY IS THE DISCRIMINANT IMPORTANT?
- The discriminant tells you the number and types
of answers - (roots) you will get. The discriminant can be ,
, or 0 - which actually tells you a lot! Since the
discriminant is - under a radical, think about what it means if you
have a - positive or negative number or 0 under the
radical. -
5WHAT THE DISCRIMINANT TELLS YOU!
Value of the Discriminant Nature of the Solutions
Negative 2 imaginary solutions
Zero 1 Real Solution
Positive perfect square 2 Reals- Rational
Positive non-perfect square 2 Reals- Irrational
6 Example 1
Find the value of the discriminant and describe
the nature of the roots (real,imaginary,
rational, irrational) of each quadratic equation.
Then solve the equation using the quadratic
formula) 1.
a2, b7, c-11
Discriminant
Value of discriminant137 Positive-NON perfect
square Nature of the Roots 2 Reals - Irrational
Discriminant
7Example 1- continued
Solve using the Quadratic Formula
8Solving Quadratic Equations by the Quadratic
Formula
Try the following examples. Do your work on your
paper and then check your answers.
9Sum and Product of Roots
10Sum Product of Roots
11Write a Quadratic Equation-Ex.1
Write a quadratic equation that has roots
12Write a Quadratic Equation Ex. 2
Write a quadratic equation that has roots
13Solve each equation. Check using sum and
product of the roots.
It CHECKS !
14Write a quadratic equation whose roots satisfy
the following conditions.
You must change the denominators to common
denominators.
15Solve the following quadratic equations and
check using the sum and products of the roots!