SOLUTION: Find all real values of p such that 2(x+6)(x-p)\] has a minimum value of -4 over all real values of x.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Find all real values of p such that 2(x+6)(x-p)\] has a minimum value of -4 over all real values of x.      Log On


   



Question 1209309: Find all real values of p such that
2(x+6)(x-p)\]
has a minimum value of -4 over all real values of x.

Answer by ikleyn(52778) About Me  (Show Source):
You can put this solution on YOUR website!
.
Find all real values of p such that 2(x+6)(x-p)
has a minimum value of -4 over all real values of x.
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Expression  2(x+6)(x-p)  represents a parabola opened upward
with the vertex  at  x= %28-6%2Bp%29%2F2,  half-way between x-intercepts -6 and p.


The y-value at the vertex is  

    2%2A%28%28-6%2Bp%29%2F2%2B6%29%2A%28%28-6%2Bp%29%2F2-p%29 = 2%2A%28%286%2Bp%29%2F2%29%28%28-6-p%29%2F2%29 = -%281%2F2%29%2A%286%2Bp%29%5E2.


We want

    -%281%2F2%29%2A%286%2Bp%29%5E2 = -4.


It gives  

    %286%2Bp%29%5E2 = 8

    6 + p = +/- sqrt%288%29

    p = -6 +/- 2%2Asqrt%282%29.


ANSWER.  There are two real numbers "p" satisfying the imposed requirements.

         They are  -6 - 2%2Asqrt%282%29  and  -6 + 2%2Asqrt%282%29.

Solved.