0\\D=(2k)^2-4*3*7=4k^2-84\\4k^2-84>0|:4\\k^2-21>0\\(k- \sqrt{21})(k+ \sqrt{21})>0\\\\k\in(-\infty;- \sqrt{21}) \cup( \sqrt{21};+\infty) " alt="3x^2+2kx+7=0\\D>0\\D=(2k)^2-4*3*7=4k^2-84\\4k^2-84>0|:4\\k^2-21>0\\(k- \sqrt{21})(k+ \sqrt{21})>0\\\\k\in(-\infty;- \sqrt{21}) \cup( \sqrt{21};+\infty) " align="absmiddle" class="latex-formula">