In this case, the denominator of the function impose the
domain of definition.
We'll impose the constraint of
existence of the function:
3x^2 - 12 different
from 0
In other words, the domain of definition will
contain x values that don't cancel the denominator.
We'll
compute the roots of the equation
3x^2 - 12 =
0
We'll divide by 3 both
sides:
x^2 - 4 = 0
Since it is
a difference of squares, we'll write it using the
formula:
a^2 - b^2 =
(a-b)(a+b)
x^2 - 4 =
(x-2)(x+2)
But x^2 - 4 = 0,
so
(x-2)(x+2) = 0
We'll put
each factor as 0:
x - 2 = 0
x
= 2
x + 2 = 0
x =
-2
The domain of definition is the real set
R, rejecting the roots of the equation from
denominator.
R - {-2 ;
+2}
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