an class=comment>%&nbsp;The&nbsp;decision&nbsp;function&nbsp;is&nbsp;quadratic,&nbsp;i.e.&nbsp;in&nbsp;2d
</span><br>
&nbsp;&nbsp;&nbsp;<span class=comment>%&nbsp;there&nbsp;exis&nbsp;two&nbsp;thresholds&nbsp;which&nbsp;determine&nbsp;three&nbsp;intervals.
</span><br>
&nbsp;&nbsp;&nbsp;
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&nbsp;&nbsp;&nbsp;D=b^2-4*a*c;
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&nbsp;&nbsp;&nbsp;<span class=keyword>if</span>&nbsp;D&nbsp;&gt;&nbsp;0,
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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;th1=(-b-sqrt(D))/(2*a);
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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;th2=