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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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atyourservice | TA , Grade 10 | Valedictorian

Posted June 26, 2014 at 6:50 AM (Answer #3)

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

saying the roots are 6 and 7 give you a clue just put them back in parentheses:
 
(x - 6) (x - 7)
 
now FOIL
 
x^2 - 7x - 6x + 42
 
combine:
 
x^2 - 13x + 42
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givingiswinning | TA , Grade 10 | Valedictorian

Posted August 15, 2014 at 11:53 PM (Answer #4)

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(x - 6) (x - 7)
 
FOIL
 
x^2 - 7x - 6x + 42
 
x^2 - 13x + 42
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taangerine | TA , Grade 11 | Valedictorian

Posted August 16, 2014 at 1:57 AM (Answer #5)

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(x - 6) (x - 7)

Using FOIL, expand the equation 

FOIL = First Outside Inside Last

x^2 - 7x - 6x + 42

Combine like terms

x^2-13x+42

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