gcse: inequalities – shading regions dr j frost ([email protected]) last modified: 5...
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GCSE: Inequalities – Shading Regions
Dr J Frost ([email protected])
Last modified: 5th October 2014
Associated Resources: GCSE-InequalitiesRegionsWorksheet.docx
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Means: x is less than or equal to 4.
x > 3Means: x is (strictly) greater than 3.
0 1 2 3 4 5
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This is known as a ‘strict’ inequality.
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x < -1Means: x is (strictly) less than -1.
-3 -2 -1 0 1 2
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x ≥ 4Means: x is greater than or equal to 4.
2 3 4 5 6 7
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x ≤ 5
2 3 4 5 6 7
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RECAP: Inequalities on a Number Line
STARTER: Solving Inequalities
−𝟐 ,−𝟏 ,𝟎 ,𝟏 ,𝟐 ,𝟑
𝒙<𝟏𝟓𝟒
𝒙<−𝟒
𝟔<𝒙 ≤𝟗
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(On your worksheet)
-10 -8 -6 -4 -2 2 4 6 8 10
8
6
4
2
-2
-4
-6
Sketch the region
representing
Think: How are the values of x constrained, and how are the values of y constrained?
can be any number greater than 2, but can be ANY value because it is not constrained.
The dotted line indicates that can’t be 2.
-10 -8 -6 -4 -2 2 4 6 8 10
8
6
4
2
-2
-4
-6
-4 < y ≤ -2
-10 -8 -6 -4 -2 2 4 6 8 10
8
6
4
2
-2
-4
-6
y ≥ x
How can we tell which way round the inequality is?Just try a point on one side, e.g. (0, 4). Is y ≥ x? Yes, so we’re on the right side.
Quickfire RegionsIs the region on the correct side of the line?
y > x + 2
2
WinFail
y > 1 - x1
WinFail
y – x > 1
1
WinFail
x + y > 11
WinFail
x > 2y - 3
1.5
y > -x
WinFail
Bro Tip: An easier way to see if the region is on the correct side is to see whether is on the smaller side of the inequality or the greater side. If the greater, we’re above.
WinFail
-10 -8 -6 -4 -2 2 4 6 8 10
8
6
4
2
-2
-4
-6
y ≤ x + 1 and x ≤ 6 and y > 2
Combining Inequalities
Bro Tip: In GCSE exam questions, the region you want is almost always the region enclosed by your 3 lines.
Question 4 Worksheet Answers
Click to Sketch >
Question 5 Worksheet Answers
Click to Sketch >
Question 6 Worksheet Answers
(𝟐 ,𝟐 ) , (𝟐 ,𝟒 ) , (𝟑 ,𝟑)?
Click to Sketch >
Question 7 Worksheet Answers
Click to Sketch >
Question 8 Worksheet Answers
3 2
Click to Sketch >
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Question 9 Worksheet Answers
𝟓𝟐−𝟓𝟔𝒙
𝟐𝟎
R
1 1
Click to Sketch >
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