# Thread: Someone care to explain? The -1 + 12?

2. ## Re: Someone care to explain? The -1 + 12?

the process is called completing the square ...

$\displaystyle -3(x^2 + 4x) - 1$

$\displaystyle \color{red}{-3}\color{black}{(x^2 + 4x} \color{red}{+4}\color{black}{) - 1} \color{blue}{+ 12}$

adding -3(4) is equivalent to adding -12 to the expression ... adding +12 balances the value of the expression.