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1819 G2X §9.2
Which exercises should we discuss on the board?
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Slide 1:
Mind map
Wiskunde
Middelbare school
havo, vwo
Leerjaar 2
This lesson contains
10 slides
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interactive quizzes
and
text slides
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Lesson duration is:
50 min
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Items in this lesson
Which exercises should we discuss on the board?
Slide 1 - Mind map
Solve 8a + 3 = 3a + 13
(show steps!)
Slide 2 - Open question
Solving equations
You can solve 8a + 3 = 3a + 13 with the balance method.
First your subtract 3a from both sides: 5a + 3 = 13
Then your subtract 3 from both sides: 5a = 10
Then divide by 5 on both sides: a = 2
So far we have seen positive, whole solutions.
Slide 3 - Slide
Solving equations
The balance method can also be used with negative numbers, fractions and decimal numbers.
We keep following the rules of the balance method:
- You can add or subtract the same term from both sides of the equal sign.
- You can multiply or divide by the same number on both sides of the equal sign.
Slide 4 - Slide
Examples
Solve: 2a + 5 = 19 - 5a
+ 5a
on both sides: 7a + 5 = 19
- 5
on both sides: 7a = 14
÷ 7
on both sides: a = 2
Slide 5 - Slide
Examples
Solve: -3r - 4 = 2r + 7
- 2r
on both sides: -5r - 4 = 7
+ 4
on both sides: -5r = 11
÷ -5
on both sides: r = -2.2
We can also solve the same equation in a different way!
Slide 6 - Slide
Examples
Solve: -3r - 4 = 2r + 7
+ 3r
on both sides: - 4 = 5r + 7
- 7
on both sides: -11 = 5r
÷ 5
on both sides: -2.2 = r
(It is common to then also write the solution as r = -2.2)
Slide 7 - Slide
Equations with brackets
If you want to solve 2(3t - 4) = -3(5t - 2) - 7
you must first remove the brackets and write each side of the equation as short as possible, before you can use the balance method.
Slide 8 - Slide
Equations with brackets
Solve: 2(3t - 4) = -3(5t - 2) - 7
Remove brackets: 6t - 8 = -15t - 1
+ 15t
on both sides: 21t - 8 = -1
+
8
on both sides: 21t = 7
÷
21
on both sides: t =
3
1
Slide 9 - Slide
HW Friday
Make and correct §9.2
Slide 10 - Slide
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