# 2TH/vwo lesson 3 - Equations/Graphs

First let's look at the steps we need to plot a linear graph
1 / 18
Slide 1: Slide
Middelbare schoolvwoLeerjaar 1

This lesson contains 18 slides, with interactive quizzes and text slides.

Lesson duration is: 50 min

## Items in this lesson

First let's look at the steps we need to plot a linear graph

Formula
Table
Graph

#### Slide 2 -Slide

Sometimes we only have a graph and not the formula.
What do we do then?

Graph
Table
Formula

#### Slide 4 -Slide

Steps
1. Find some values on the graph that can be read off easily
2. Make a table
4. Make a linear formula

#### Slide 5 -Slide

Remember this?
• Make a table with values of t on the top row and corresponding values of N on the bottom row
t    0    1      2    3    4
N  2   2.5   3  3.5  4
• Use the table to find the y-intercept (value of N when t=0)  so here y-intercept = 2
• Use the table to calculate the gradient           increase in N /increase in t = 1/2 or 0.5
• Fill these values into the standard formula y=ax + b where a is the gradient and b is the y-intercept
• y = 0.5x + 2

#### Slide 6 -Slide

What is the difference between a formula and an equation?
Formula - is a rule about how you calculate for all values
Equation - When a formula has a specific answer.
You can solve the equation to find which value of the variable gives the correct answer.

#### Slide 7 -Slide

How do you find a value that is not easy to read off a graph?
Use the steps above to find the linear formula
Write down the corresponding equation
Solve the equation

#### Slide 8 -Slide

The graph corresponds to the growth of a seedling. After how many days is the seedling 50cm high?

Graph
Table
time in days (t)       0      2     4     6
height in cm  (H)    5    10    15   20

y-intercept = 5

formula: H = 5 + 2.5t
but H=50
so equation 50 = 5 + 2.5t
Solving
45 = 2.5t
45/2.5 = 18 = t
so after 18 days the seedling is 50cm high

#### Slide 9 -Slide

What is a formula?

#### Slide 10 -Open question

What is an Equation?

#### Slide 11 -Open question

How many coins weigh 875 grams?
A
75
B
7.5
C
100
D
65

#### Slide 12 -Quiz

Here is the graph for the formula
b = 10 + 5t

Solving the equation
21.50 = 10 + 5t
gives
t=?
A
3.2
B
2.3
C
11.5
D
5

#### Slide 13 -Quiz

L= 3m +12
L = 4m + 12
L = 1/3m + 12
What are the values of m when L=48?
A
m=3, m=4, m=1/3
B
m=16, m=12, m= 144
C
m=1/3, m=4, m=3
D
m=12, m=9, m=108

#### Slide 14 -Quiz

More than 1 mistake
ex 15,17,18
ex 38,40, T3
ex B4,B5

Only 1 mistake
Ex 38,40, T3
ex B4,B5

All correct
ex T3,B4,B5

#### Slide 17 -Slide

What do you remember from today's lesson?

Graphs