Question 922838
{{{ x = 2i }}}
{{{ x = -2i }}}
{{{ f(x) = ( x - 2i )*( x + 2i ) }}}
{{{ f(x) = x^2 - 4*i^2 }}}
{{{ f(x) = x^2 + 4 }}}
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check:
solve with quadratic formula
{{{ x = (-b +- sqrt( b^2 - 4*a*c ))/(2*a) }}}
{{{ a = 1 }}}
{{{ b = 0 }}}
{{{ c = 4 }}}
{{{ x =  sqrt( - 4c )/2 }}}
{{{ x = ( 2*sqrt(4)*i ) / 2 }}}
{{{ x = 4i / 2 }}}
{{{ x = 2i }}}
and also:
{{{ x = -2i }}}
OK