# 6.2 Quadratic formulas

Quadratic Formulas
Today you will learn:
What are quadratic formulas and how can I use them?
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Slide 1: Slide
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This lesson contains 19 slides, with interactive quizzes and text slides.

## Items in this lesson

Quadratic Formulas
Today you will learn:
What are quadratic formulas and how can I use them?

#### Slide 1 -Slide

Yesterday you learned
Squares
7² = 49
Squares of negative numbers
-7² = -49
(-7)² = 49
Square roots
√49 = 7

Calculate:
6² + (-3)²
A
-45
B
27
C
45
D
-27

Calculate:
-5 * -8²
A
78400
B
320
C
-320
D
169

Calculate:
-1 - 5 * (-2)²
A
-21
B
-24
C
19
D
20

Calculate:
√16 - √49
A
-5.7
B
3
C
28
D
-3

Calculate:
√4 * √1 * √0
A
0
B
1
C
2
D
Not possible

#### Slide 7 -Quiz

Quadratic Formulas
Formulas with letters:
y = -2x + 8

Quadratic formulas:
y = -2x² + 8

#### Slide 8 -Slide

An example
This row of shapes can be extended.
How many dots does shape 5 consist of?
And shape 6?
And shape 10?

#### Slide 9 -Slide

An example
-What is the number of the shape with 144 dots?
-How do you calculate the number of dots in a shape with number n?
-What is the formula for this row?

#### Slide 10 -Slide

An example
What is the formula for this row?
a = n²

This is an example of a quadratic formula.

#### Slide 11 -Slide

Using quadratic formulas
a = n²
What is a if you have n = 3?
And if n = 20?
And if n = -5?

#### Slide 12 -Slide

Using quadratic formulas
a = n²
What is a if you have n = 3?
a = 3² = 3*3 = 9
And if n = 20?
a = 20² = 20*20 = 400
And if n = -5?
a = (-5)² = -5 * -5 = 25

#### Slide 13 -Slide

Formula: a = n²
Calculate a when n = 8
A
8
B
16
C
64
D
640

#### Slide 14 -Quiz

Formula: y = 3x² - 6
Calculate y when x = 4
A
42
B
48
C
54
D
138

#### Slide 15 -Quiz

Formula: y = 3x² - 6
Calculate y when x = -5
A
-81
B
81
C
-69
D
69

#### Slide 16 -Quiz

Formula: y = (x+5)²
Calculate y when x = 3
A
28
B
36
C
64
D
225

#### Slide 17 -Quiz

Formula: y = (x+5)²
Calculate y when x = -9
A
-16
B
16
C
45
D
-45

#### Slide 18 -Quiz

Now you know about Quadratic formulas!

Homework today: 3-14
Homework Thursday: 15-24, NOT 17, 20