Question 905695
{{{y=x^2+6x-3}}}
Take the coefficient of x terms, halve it, square it and add and subtract it to the equation.
{{{y=x^2+6x+(3)^2-(3)^2-3}}}
Simplify,
{{{y=(x^2+6x+9)-9-3}}}
{{{y=(x+3)^2-12}}}