solving quadratic equations by completing the square 
Possible Duplicate:
How to “Re-write completing the square”: $x^2+x+1$ 

$b^2-4b+4=16$ can someone help me solve this equation. All the steps please.

if $ax^2+bx^2+c=0$ then
$$
0=a\Big(x^2+\frac{b}{a}x\Big)+c
=a\Big(x^2+\frac{b}{a}x+\frac{b^2}{4a^2}-\frac{b^2}{4a^2}\Big)+c
=a\Big(x+\frac{b}{2a}\Big)^2+c-\frac{b^2}{4a}
$$
hence
$$
\Big(x+\frac{b}{2a}\Big)^2=\frac{b^2-4ac}{4a^2}
$$
and
$$
x=-\frac{b}{2a}\pm\sqrt{\frac{b^2-4ac}{4a^2}}=\frac{-b\pm\sqrt{b^2-4ac}}{2a}
$$
