Question 961440
{{{ x^2 + 6x + C = 0 }}}
Complete the square
{{{ x^2 + 6x + (6/2)^2 = C + ( 6/2)^2 }}}
{{{ x^2 + 6x + 9 = C + 9 }}}
{{{ ( x + 3 )^2 = C + 9 }}}
Take the square root of both sides
{{{ x + 3 = sqrt( C + 9 ) }}}
{{{ x = -3 +- sqrt( C + 9 ) }}}
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If {{{ C > -9 }}} you get 2 values for {{{ x }}}
If {{{ C = -9 }}} you get 1 value for {{{ x }}}
If {{{ C < -9 }}} you get 2 complex values for {{{ x }}}
( I just added this info -you don't need it )