Thursday, January 9, 2014

Given the roots 6 and 7, determine the quadratic equation?

To determine the quadratic equation, we'll use Viete's
relations:


x1 + x2 = S, where x1 = 6 and x2 =
7


x1 + x2 = 6+7


S =
13


x1*x2 = P


P =
6*7


P = 42


The quadratic
equation is:


x^2 - Sx + P =
0


x^2 - 13x + 42 = 0


The
quadratic equation is:


x^2 - 13x + 42 =
0


Another method of creating the quadratic when knowing the
roots is to write the equation as a product of linear
factors;


(x-x1)(x-x2) =
0


(x-6)(x-7) = 0


We'll remove
the brackets:


x^2 -6x - 7x +42 =
0


We'll combine like terms and we'll get the quadratic
equation:


x^2 - 13x + 42 =
0

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