# functions question

• June 29th 2008, 08:46 AM
petedude
functions question
Regarding f(x) = 3x(squared) -x -2...

If x=2, what is f(x)?

Supposedly, I'm to factor something here to get the answer.

I've got a handful of questions like this, and about four sub-chapters pending after it. . . all due by tomorrow night!
• June 29th 2008, 09:23 AM
nikhil
Here it is
Quote:

Originally Posted by petedude
Regarding f(x) = 3x(squared) -x -2...
If x=2, what is f(x)?

f(x) will always be 3x^2-x-2 as f(x) is pre defined so i guess you wanted to ask f(2) or value of f(x) at x=2 which is given as
f(2)=3(2)^2-2-2=12-4=8
• June 29th 2008, 12:58 PM
masters
(c) If f(x)= -2, what is x? What point(s) are on the graph of f ?

$f(x)=3x^2-x-2$

$f(x)=3x^2-x-2=-2$

$3x^2-x=0$

$x(3x-1)=0$

$x=0 \ \ or \ \ x=\frac{1}{3}$

Two points on the graph would be the x-intercepts (0, 0) and (1/3, 0).

(d) What is the domain of f ?

$D=\{x|x\in\Re\}$ (i.e. all real numbers)

(e) List the x-intercepts of $f(x)=3x^2-x-2$

$3x^2-x-2=0$

$(x-1)(3x+2)=0$

$x=1 \ \ or \ \ x=-\frac{2}{3}$

$x-intercepts \ \ are \ \ (1, 0) \ \ and \ \ (-\frac{2}{3}, 0)$

(f) List the y-intercept, if any, of the graph of f.

$f(x)=3x^2-x-2$

$f(0)=3(0)^2-2(0)-2 = -2$

$y-intercept = -2$