Chapter
9
9.3 Quadratic Inequalities in Two
Variables
Focus On ...
• explaining how to use test points to find the
solution to an inequality
• explaining when a solid or a dashed line should
be used in the solution to an inequality
• sketching, with or without technology, the
graph of a quadratic inequality
• solving a problem that involves a quadratic
inequality
At this point in the course you all
should be able to graph this:
y = x2 - 4x - 5
But can you graph these?
y ! x2 - 4x - 5
y " x2 - 4x - 5
Warm-Up:
Graphing Linear and Quadratic Equations
1. 2x - 5y = 10
1. y = x2 - 4x - 5
2. -2x - 3y = 12
2. y = x2 - 9
3. -y = -3x + 9
3. y = -1/2x2 - 4
4. 0 = 2x + 3y -15
4. y = -2(x + 4)2
2
y = x - 4x - 5
y ! x2 - 4x - 5
y " x2 - 4x - 5
2. y < x2 - 9
3. y > -1/2x2 - 4
4. y " -2(x + 4)2
9.3
2
Answer
Graph y " –x + 2x + 4.
(0, 3)
V(-2, 1)