I am beginning to work with

**Polynomial**,

**Rational**, and

**Quadratic** functions...

I can understand most of it but I am having issues trying to understand who it works if written like this,

$\displaystyle f(x)=x^2+2x$

I am told that the first thing to do is completing the Sqr, by adding one

*and* subtracting one, thus;

$\displaystyle f(x)=x^2+2x+1-1$

$\displaystyle x^2+2x+1=(x+1)^2-1$

$\displaystyle x+1=0$

$\displaystyle x=-1$

and so my vertex is (-1,-1)

but now how about the $\displaystyle X$ and the $\displaystyle Y$ coordinates?

Thank you and sorry for such a long post.