Adapted from Walch Education
IDENTIFYING THE DOMAIN OF A
QUADRATIC FUNCTION
5.5.2: Identifying the Domain of a
Quadratic Function
DOMAIN

The domain of a function is all input values that
satisfy the function without restriction.

This is expressed by showing that the input
values exist from negative infinity to infinity as
-¥ < x < ¥.
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5.5.2: Identifying the Domain of a
Quadratic Function
PRACTICE # 1
Describe the domain of the quadratic function
g(x) = 1.5x2.
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5.5.2: Identifying the Domain of a
Quadratic Function
SKETCH A GRAPH OF THE FUNCTION
4
5.5.2: Identifying the Domain of a
Quadratic Function
DESCRIBE WHAT WILL HAPPEN IF THE
FUNCTION CONTINUES

Looking at the function, you can see that the
function will continue to increase upward and
the function will continue to grow wider.

Growing wider without end means that the
domain of this function is all real numbers as
x increases to infinity and decreases to
negative infinity, or -¥ < x < ¥.
5
5.5.2: Identifying the Domain of a
Quadratic Function
YOUR TURN…

Describe the
domain of the
function graphed
at right.
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Dr. Dambreville
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