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Title: Solving quadratic inequalities (Algebra )
Lesson objectives/ Lesson aim
By the end of the lesson, you will:
Solve quadratic inequalities graphically.
Lesson goals/Learning outcomes
Inequalities show the relationship between two
expressions that are not equal to one another.
The symbols used for inequalities are <, >, ≤, ≥.
(continue on slide no-7)
Starter/ Do Now activity/ Warmer
Slide no -5
Scaffolder practice ( You do)
Slide 11
Instruction and Modelling (I do/We do)
Slide 6 to 10
Lesson at a glance
Vocabulary
Algebra, Inequalities, Equations, Expression, Equation
Quadratic functions, Root, Coefficient, Factors etc
Checking for understanding
Slide 12
Plenary/Exit Ticket
Slide 15 and 16
Extension Task/Challange
Slide 13&14
Title: Solving quadratic inequalities (Algebra )
Lesson objectives:
By the end of the lesson, you will:
Solve quadratic inequalities graphically.
Lesson Goals/ Learning outcome
To achieve this, you will need to know:
• Inequalities show the relationship between two expressions that are not equal to one another.
• The symbols used for inequalities are <, >, ≤, ≥.
• The process to solve inequalities is the same as the process to solve equations
• That extra care should be taken when the unknown in an inequality has a negative coefficient.
• An inequality can be represented graphically as a region on one side of a line.
• Inequalities that use < or > symbols are plotted with a dashed line to show that the line is not included
in the region.
• How to find the roots of a quadratic function
• How to sketch a graph of a quadratic functions
• How to rearrange quadratic equations if they are not equal to zero.
• How to solve quadratic inequalities in one variable, by factorising and sketching the graphs
• How to solve a quadratic inequality (a = 1 and a>1)
Vocabulary
• Algebra
• Inequalities
• Equations
• Expression
• Equation
• Quadratic functions
• Root
• Coefficient
• Factors etc
STARTER/Retrieval/Warmer
Solve the following quadratic equations
Instruction and Modelling(I do/We do)
Solve x² + 6x + 8 ≤ 0
Step 1: Start
by solving the
inequality as an
equation
Solve x² + 6x + 8 = 0
(x + 4)(x + 2) = 0
x = -4, x = -2
Teacher Example 1- I do
These are the point
where the quadratic
graph intersects the
-axis
Step 2: Now we
need to sketch
the graph
Solve x² + 6x + 8 ≤ 0
This means: for what values
of x is the graph below the -
axis?
Teacher Example 1
continued
Original question:
Step 3: Highlight the
part of the graph
below the -axis
The graph is below the -axis
between -4 and -2.
Let’s write that as an
inequality…
ANSWER:
Solve x²+ 6x + 8 ≥ 0
What’s
different
this time?
Solution on the next slides
Teacher Example 2 - We do
Solve x² + 6x + 8 ≥ 0
Step 1: Start by
solving the
inequality as an
equation
Solve x² + 6x + 8 = 0
(x + 4)(x + 2) = 0
x = -4, x = -2
Teacher Example 2
These are the point
where the quadratic
graph intersects the
-axis
Step 2: Now we
need to sketch
the graph
Solve x² + 6x + 8 ≥ 0
This means: for what values
of x is the graph above the -
axis?
Teacher Example 2
continued
Original question:
Step 3: Highlight the
part of the graph
above the -axis
We have highlighted TWO
separate parts of the graph,
so need to write our answer as
TWO separate inequalities
ANSWER: and
What can you say
about the values of
points in this region?
What can you say
about the values of
points in this
region?
Scaffolded practice (You do)
Complete the grid to solve the inequalities.
Check for understanding/ Assessment opportunities
In pairs, summarise the steps needed to
solve a quadratic inequality
Step 1 Start by solving the inequality as a quadratic equation equal to 0
Step 2 Sketch the graph. Your solutions are the points where the
quadratic graph intersects the-axis
Step 3 Consider the original inequality- highlight the correct part of the
graph
Step 4 Write your solutions as an inequality using your graph
Did you
discuss
these
points?
TURN
AND
TALK
Extension Work (You do/independent practice)
𝑥
𝑦
− 4 −1
𝑦 =(𝑥+4)(𝑥 +1)
or
𝑥
𝑦
−3 3
𝑦=(𝑥+3)(𝑥 −3)
− 3 < 𝑥< 3
? ?
Solve Solve
EXTENSION:
Solve
Solve
?
?
1
2
Exit Ticket – Spot the mistakes
SILENT
SOLO
Only one answer is
correct! You need to
identify the
mistakes and decide
which is the correct
answer – happy
sleuthing!
Model model Lesson for teachers of igcse