Solving Quadratic Equations and Quadratic Formula

​Solving Quadratic Equations by Using the Quadratic Formula

Objective:

​Solve quadratic equation by:  (d) quadratic formula

 

​

Explore:

​Smartphones are getting "smarter" and more versatile.

Can you​ name 10 products that a smartphone can replace?

​

​

​

​

​

​​

​

​

​

​

​

​

​Image credit to: samsung.com

​The Quadratic Formula

​Steps:

​1. Write the equation in standard form.

2.​ Identify the numerical values of the coefficients a, b, and c.

3. Write ​the quadratic formula.

4. Substitute the numerical values for a, b, and c in the quadratic formula.

5. Simplify to get the exact solution

6. Check the solution.​

​

​

​Example 1: Solve x² - x - 42 = 0 using quadratic formula.

​Solution:

​Example 1: Solve x² - x - 42 = 0 using quadratic formula.

​Solution:

​Example 2: Solve x² + 3x + 6 = 0 using quadratic formula.

​Solution:

Multiple Choice

Identify the value of a, b, and c given the quadratic equation 3x - 5x² = 10.

• a = 3

  b = -5

  c = 10

• a = -5

  b = 3

  c = -10

• a = -3

  b = 5

  c = -10

• a = 10

  b = -3

  c = - 5

Multiple Choice

Solve for x.

x² + 3x - 4 = 0

• x = 2 and x = - 2

• x = - 4 and x = 1

• x = 4 and x = - 1

• x = -2 and x = -2

​Worktext Reference

​Oronce O.A., Mendoza M.O. (2019). E-Math Worktext in Mathematics 9, Manila, Philippines: REX Bookstore Inc.

 

Reference

​ Nivera G.C., Lapinid M.R.C. (2018). Grade 9 Mathematics Patterns and Practicalities 9, Makati City, Philippines: Salesiana Books by Don Bosco Press,