SOLUTION: the sum of the roots of a quadratic equation is -4. if one of the roots is 7, how would you determine the equation? write the equation.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: the sum of the roots of a quadratic equation is -4. if one of the roots is 7, how would you determine the equation? write the equation.      Log On


   

Question 1164777: the sum of the roots of a quadratic equation is -4. if one of the roots is 7, how would you determine the equation? write the equation.
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
By this formula:

 

Put -4 for the sum of roots.



One root is given as 7.
Let the other root be R:

Then 7 + R = -4
         R = -4 - 7
         R = -11

Put (7)(-11)=-77 for the product of roots:

 

Simplify the signs:

 

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Check by factoring:

     x² + 4x - 77 = 0
  (x + 11)(x - 7) = 0

x + 11 = 0;   x - 7 = 0
     x = -11;     x = 7     

Edwin