Question 94545
Quadratic formula{{{(-b+-sqrt(b^2-4ac))/2a}}}
Let k=c in the formula
If{{{b^2-4ak}}}is negative then the answer will not be a real number because the square root of a negative number is not a real number.
a=3 b=-6 c=k
{{{b^2=-6^2=36 }}} so  must be {{{-4ak>=-36}}}.
{{{-4*3*k>=-36}}}
{{{-12k>=-36}}}
divide both sides by -12.  {{{k<=3}}} 
So k must be greater than {{{-infinity}}}and less than or equal to 3
{{{-infinity<k>=3}}}
EdJones