# cut the y intercept

• Dec 10th 2009, 12:16 PM
wolfhound
cut the y intercept
where does the function cut the yintercept f(x) =
$x^3 -3x^2 -9x +2$

+2?

or when I get the f '(x) $3x^2 -6x -9$ -9?
• Dec 10th 2009, 12:17 PM
stapel
I've never heard that terminology. I will guess that "cut the y-intercept" means something like "cuts" (or crosses) "the y-axis". If this is correct, then you need to plug zero in for x to find the y-value of the y-intercept. (Wink)

I don't know what you're trying to do with the derivative, so I'm afraid I cannot comment on that. Sorry! (Blush)
• Dec 10th 2009, 12:43 PM
wolfhound
Quote:

Originally Posted by stapel
I've never heard that terminology. I will guess that "cut the y-intercept" means something like "cuts" (or crosses) "the y-axis". If this is correct, then you need to plug zero in for x to find the y-value of the y-intercept. (Wink)

I don't know what you're trying to do with the derivative, so I'm afraid I cannot comment on that. Sorry! (Blush)

Hello (Happy)
Yes in Ireland we say 'cuts the y- intercept'or crosses
do I plug 0 into the original cubic expression?
• Dec 10th 2009, 01:29 PM
Raoh
Quote:

Originally Posted by wolfhound
Hello (Happy)
Yes in Ireland we say 'cuts the y- intercept'or crosses
do I plug 0 into the original cubic expression?

calculate f(0).
(Happy)
• Dec 10th 2009, 03:06 PM
BabyMilo
Quote:

Originally Posted by wolfhound
where does the function cut the yintercept f(x) =
$x^3 -3x^2 -9x +2$

+2?

or when I get the f '(x) $3x^2 -6x -9$ -9?

yes you are right. +2 is the answer.

Here is a graph.
• Dec 10th 2009, 03:14 PM
wolfhound
Quote:

Originally Posted by BabyMilo
yes you are right. +2 is the answer.

Here is a graph.

Thanks,nice graph
(Bow)