The parabolae <em>b</em>, <em>d</em> and <em>f</em> seen in the <em>real</em> coordinate plane have <em>complex</em> roots.
<h3>What is the graphical criterion to determine what second order polynomial has complex roots?</h3>
<em>Second order</em> polynomials are <em>algebraic</em> equations of the form:
(1)
Where:
- <em>a</em>, <em>b</em>, <em>c</em> - Coefficients
- <em>x</em> - Independent variable
- <em>y</em> - Dependent variable
A value of <em>x</em> is a root of the polynomial for <em>y = 0</em>, which can <em>real</em> or <em>complex</em> but not both according to the discriminant of the <em>quadratic</em> formula. If the polynomial has no <em>real</em> roots, then it does not pass through the <em>x</em>-axis in the <em>real coordinate</em> plane.
Therefore, the parabolae <em>b</em>, <em>d</em> and <em>f</em> seen in the <em>real</em> coordinate plane have <em>complex</em> roots. 
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