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

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essesy | Student, College Freshman | eNoter

Posted January 22, 2011 at 3:12 AM via web

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

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giorgiana1976 | College Teacher | Valedictorian

Posted January 22, 2011 at 3:15 AM (Answer #1)

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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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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted January 22, 2011 at 3:17 AM (Answer #2)

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The roots of a quadratic equation are given as 6 and 7. This means that x - 6 = 0 and x - 7 = 0

We can write ( x - 6)( x - 7) = 0

=> x^2 - 6x - 7x + 42 = 0

=> x^2 - 13x + 42 = 0

Therefore the required quadratic equation is

x^2 - 13x + 42 = 0

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