5.2 The quadratic formula jko

• Wiskunde
• Middelbare school
• havo, vwo
• Leerjaar 3

5-2 Using the quadratic formula

What you need: - Textbook, writingbook, iPad - Pen, pencil, geotriangle - Calculator

                         Lesson goals

Use the quadratic equation to solve equations.

What if factorisation doesn't work

You use the quadratic equation

First write the equation in the standard form...

So actually the quadratic equation is

but to simplify the calculation we use D

1. a=1 b=5 c=3
2. a=3 b=-5 c=1
3. a=1 b=-5 c=3
4. a=3 b=5 c=1

x​2​​−5x+3

Calculate the Discriminant

Discriminant=b​2​​−4⋅a⋅c

1. -7
2. 13
3. 21
4. 37

x​2​​−5x+3

Solve the equation

x​1​​=​2⋅a​​(−b+√​D​​​)​​

x​2​​=​2⋅a​​(−b−√​D​​​)​​

1. x=4,3 or x=-0,7
2. x=4,3 or x=0,7
3. x=-4,3 or x=0,7
4. x=-4,3 or x=-0,7

1. -1
2. 1

−x​2​​−4x+12

Calculate D

1. -32
2. 32
3. 60
4. 64

−x​2​​−4x+12

Solve the equation

1. x=6 or x=2
2. x=-6 or x=2
3. x=6 or x=-2
4. x=-6 or x=-2

Try on your own

1, 2, 5 and 7

RULES:

• In your writingbook
• Start with writing down the letters. Start with D, a,b,c,
• 
  

Extra excercise: Bettermarks

Challenge: Do both!

HW - Chapter 5: 10-15