how do you complete the square

Question

anonymous · Answer

depends on the context. are you trying to solve a quadratic equation?

anonymous · Answer

no parabolas

anonymous · Answer

they are the same thing

anonymous · Answer

ah then you want to find the vertex by comleting the square. i.e. you want to write 
$$y=ax^2+bx+c$$ as 
$$y=a(x-h)^2+k$$ right

anonymous · Answer

$$x^2 +bx+c=x^2+bx+(b/2)^2-(b/2)^2+c=(x+b/2)^2+c-(b/2)^2$$

anonymous · Answer

here is an easy method with an example. 
the vertex is always where 
$$x=-\frac{b}{2a}$$ so if i see 
$$y=x^2-6x+5$$ i know the first coordinate of the vertex will be 
$$-\frac{6}{2(-1)}=3$$ and the second coordinate will be what i get when i replace x by 3 namely -4

so i know it is 
$$y=x^2-6x+5=(x-3)^2-4$$

anonymous · Answer

here is another method.  if you have 
$$y=ax^2+bx+c$$ you can rewrite as 
$$y=a(x^2+\frac{b}{a}x)+c$$ and then write 
$$y=a(x+\frac{b}{2a})^2+c-\frac{b^2}{4a}$$ but that seems unnecessarily complicated