Question 281278
I like to use completing the square
{{{a^2 + 12a + 36 = 0}}}
Note that this is in the form
{{{a^2 + 2*6a + 6^2 = 0}}}
The left side is a perfect square:
{{{(a + 6)^2 = 0}}}
This equation has a double root which is
{{{a = -6}}}
check:
{{{a^2 + 12a + 36 = 0}}}
{{{(-6)^2 + 12*(-6) + 36 = 0}}}
{{{36 - 12*6 + 36 = 0}}}
{{{72 - 72 = 0}}}
{{{0 = 0}}}
OK