# Thread: cut the y intercept

1. ## cut the y intercept

where does the function cut the yintercept f(x) =
$\displaystyle x^3 -3x^2 -9x +2$

+2?

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

2. 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.

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

3. 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.

I don't know what you're trying to do with the derivative, so I'm afraid I cannot comment on that. Sorry!
Hello
Yes in Ireland we say 'cuts the y- intercept'or crosses
do I plug 0 into the original cubic expression?

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

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

+2?

or when I get the f '(x) $\displaystyle 3x^2 -6x -9$ -9?
yes you are right. +2 is the answer.

Here is a graph.

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

Here is a graph.
Thanks,nice graph