配方法计算器

Your input: complete the square in $$$x^{2} + 6 x$$$.

Add and subtract $$$9$$$:

$$$x^{2} + 6 x=x^{2} + 6 x + {\color{red}{\left(9\right)}} - {\color{red}{\left(9\right)}}$$$

Complete the square:

$$$-9 + {\color{red}{\left(x^{2} + 6 x + 9\right)}}=-9 + {\color{red}{\left(x + 3\right)^{2}}}$$$

Answer: $$$x^{2} + 6 x=\left(x + 3\right)^{2} - 9$$$.