Question 1200746
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                Trace attentively my steps


<pre>

{{{ (-12 + sqrt(-45)) / 24 }}} = {{{(-12 + sqrt(9*(-5)))/24}}} = {{{(-12+3*sqrt((-5)))/24}}} = {{{(-4 + i*sqrt(5))/8}}},  


where  " i "  is the  " imaginary unit ",  i^2 = -1.
</pre>

Solved.