Question 609378
{{{ x^2 - 4x = -3 }}}
You can complete the square
Take 1/2 of the coefficient of {{{x}}},
square it, and add it to both sides
{{{ x^2 - 4x + (-4/2)^2 = -3 + (-4/2)^2 }}}
{{{ x^2 - 4x + 4 = -3 + 4 }}}
{{{ ( x - 2 )^2 = 1 }}}
Take the square root of both sides
{{{ x-2 = 1 }}}
{{{ x = 3 }}}
and, also
{{{ x-2 = -1 }}}
{{{ x = 1 }}}
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Check by plugging the answers back into equation
{{{ x^2 - 4x = -3 }}}
{{{ 3^2 - 4*3 = -3 }}}
{{{ 9 - 12 = -3 }}}
{{{ -3 = -3 }}}
and
{{{ x^2 - 4x = -3 }}}
{{{ 1^2 - 4*1 = -3 }}} 
{{{ 1 -4 = -3 }}}
{{{ -3 = -3 }}}
OK