# domain of functions 4

• January 21st 2010, 11:54 AM
bastropgarl
domain of functions 4
how do you find the domain of the function f(x)=the square root of 3x-2
• January 21st 2010, 11:56 AM
Jhevon
Quote:

Originally Posted by bastropgarl
how do you find the domain of the function f(x)=the square root of 3x-2

the domain of a function is the set of all input values (in this case, x-values) for which the functions is defined.

$\sqrt x$ is defined for all real numbers $x$ such that $x \ge 0$.

what do you think the domain off your function is?
• January 21st 2010, 11:59 AM
bastropgarl
x is greater then or equal to -two over three
• January 21st 2010, 12:02 PM
e^(i*pi)
Quote:

Originally Posted by bastropgarl
x is greater then or equal to -two over three

Not -2/3 as $f(-0.5) = \sqrt{-0.5}$

2/3 is the right magnitude but consider the sign
• January 21st 2010, 12:15 PM
bastropgarl
sorry but im still not grasping this
• January 21st 2010, 12:18 PM
Jhevon
Quote:

Originally Posted by bastropgarl
sorry but im still not grasping this

as e^(i*pi) said, all you needed to do was change the sign...

The domain is all real $x$ so that

$3x - 2 \ge 0$

$\Rightarrow 3x \ge 2$

$\Rightarrow x \ge \frac 23$
• January 21st 2010, 12:24 PM
e^(i*pi)
Quote:

Originally Posted by bastropgarl
sorry but im still not grasping this

The equation to solve is the one posted by Jhevon immediately above.

When I did f(-0.5) that was to prove that $x \geq -\frac{2}{3}$ is not correct by picking a value of x that is greater than -2/3. The negative result shows it's incorrect