Question 177320
{{{x = (-(-12) +- sqrt( (-12)^2-4*1*84 ))/(2*1) }}} 


{{{x = (12 +- sqrt( -192 ))/2 }}} 


But you can't take the square root of a negative number, so use the fact that the imaginary number i is defined as {{{i^2 = -1}}}:


{{{x = (12 +- sqrt( i^2(192) ))/2 }}} 



{{{x = (12 +- i*sqrt( 192 ))/2 }}} 


{{{x = (12 +- i*sqrt( 64*3 ))/2 }}} 


{{{x = (12 +- 8i*sqrt( 3 ))/2 }}} 


{{{x = 6 +- 4i*sqrt( 3 ) }}}