Explanation:
Complex number
A complex number is a number consisting of a real part and an imaginary part. Complex numbers extend
the idea of the one-dimensional number line to the two-dimensional complex plane by using the number line for
the real part and adding a vertical axis to plot the imaginary part.
A complex
number can be visually represented as a pair of numbers forming a vector on a
diagram called an Argand diagram, representing the complex plane. Re is the real axis, Im is the imaginary axis, and i is the square root of -1.
http://en.wikipedia.org/wiki/Complex_number
In mathematics, a quadratic equation is a polynomial equation of the second degree. The general form is
where x represents a variable or an unknown, and a, b, and c are constants with a ≠ 0. (If a = 0, the equation is
a linear equation.)
The constants a, b, and c, are called respectively, the
quadratic coefficient, the linear coefficient and the constant term or free term. The term
"quadratic" comes from quadratus, which is the Latin word for "square".
Quadratic equations can be solved by factoring, completing the square, graphing, Newton's method, and using the quadratic formula
Quadratic
formula
A quadratic equation with real or complex coefficients has two solutions, called roots. These two solutions may
or may not be distinct, and they may or may not be real.
The roots are given by the quadratic formula
where the symbol
"�" indicates that both
are solutions of the quadratic equation.
(Our solved example in mathguru.com uses this concept)
Discriminant
In the above
formula, the expression underneath the square root sign is called the discriminant of the quadratic equation, and
is often represented using an upper case Greek delta
A quadratic
equation with real coefficients can have either one or two distinct real roots, or
two distinct complex roots. In this case the discriminant determines the number
and nature of the roots. There are three cases:
•
If the discriminant is positive, then there are two distinct
roots, both of which are real numbers:
For
quadratic equations with integer coefficients, if the discriminant is
perfect squares, then the roots are rational numbers-in other cases
they may be quadratic irrationals.
•
If the discriminant is zero, then there is exactly one distinct real root,
sometimes called a double root:
•
If the discriminant is negative, then there are no real roots. Rather, there are two distinct
(non-real) complex roots, which are complex conjugates of each other:
where i is the imaginary unit.
Thus the roots are distinct if and only if the discriminant is
non-zero, and the roots are real if and only if the discriminant is
non-negative.
(Our solved example in mathguru.com uses
this concept)
http://en.wikipedia.org/wiki/Quadratic_equation
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above explanation is copied from Wikipedia, the free encyclopedia and is
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License.