3Tvwo § 4.3 The quadratic formula

• Wiskunde
• Middelbare school
• havo
• Leerjaar 3

8-2 Using the quadratic formula

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

Schoolbags in the cuboard

Phones in the phonebag

Bluetooth 

- ON

- VPN off

                         Lesson goals

1. Learn the quadratic formula.

2. Use this to solve quadratic equations.

What if factorisation doesn't work

You use the quadratic eqution

First write the equation in the standard form...

ATTENTION!

COPY on a new page in your NOTEBOOK

the content of the previous slide.

Write it clear and neatly, because you will use this for the coming exercises in this LESSON UP!

So actually the quadratic equation is

but to simplify the calculation we use D

ATTENTION!

Once more:

COPY  slide number 6 in your NOTEBOOK!

You will need this very soon.

Do you have no clue what to do, yet?

Don't worry, let's do one together.

Next slide, please!

Attention for 12c:

1.Do not round your answers.

Give the answers as ROOTS !!

2. Sit on your own. You only learn it by doing it yourself!

12a

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

12b

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

12c

1. x=(5 + root13):2 or x=(5- root13) : 2
2. x= 5 + root 13 :2 or x= 5 - root 13 :2
3. x= 4,3 or x=0,7
4. x=-4,3 or x=-0,7

One useful TIP:

If the ROOT in your answer comes out, then write down the result.

So change ROOT 64 into 8, ROOT 81 into 9, etcetera.

13a

1. -1
2. 1

13b

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

13c

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
• Use: Textbook
• Discussion when you are stuck is allowed

Extra excercise: none

Challenge: 16

HW - correct your mistakes