# x and y intercepts

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• May 19th 2008, 09:47 AM
zdenka
x and y intercepts
Can someone help me find x intercept for

f(x) = 1 - 3(-x-2)2
(the last 2 means square, not sure how to do upper case here)

I have been stuck with this one for couple of hours.

Thanks everyone. This is my first post I am glad I found some on-line help.
• May 19th 2008, 10:23 AM
Moo
Hello,

Quote:

Originally Posted by zdenka
Can someone help me find x intercept for

f(x) = 1 - 3(-x-2)2
(the last 2 means square, not sure how to do upper case here)

I have been stuck with this one for couple of hours.

Thanks everyone. This is my first post I am glad I found some on-line help.

An y intercept is a point where x=0.

$f(0)=1-3(-0-2)^2=1-3(-2)^2=1-3 \cdot 4=-11$
So the point $(0~,~-11)$ is an y intercept.

An x intercept is a point where y=0.

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

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

$(x+2)^2=\frac 13$

$\implies x+2=\pm \frac{1}{\sqrt{3}}$
• May 19th 2008, 10:31 AM
zdenka
thank you that looks great. I got stuck on the last line!!!