SOLUTION: Find all values of $p$ such that$$2(x+4)(x-2p)$$has a minimum value of $-18$ over all real values of $x$. (In other words, we cannot have $x$ be nonreal.)

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Find all values of $p$ such that$$2(x+4)(x-2p)$$has a minimum value of $-18$ over all real values of $x$. (In other words, we cannot have $x$ be nonreal.)      Log On


   



Question 1040895: Find all values of $p$ such that$$2(x+4)(x-2p)$$has a minimum value of $-18$ over all real values of $x$. (In other words, we cannot have $x$ be nonreal.)
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
The x-value that will give the minimum value will just be the average of the two roots, namely -4 and 2p. Their average is %28-4%2B2p%29%2F2+=+p-2.
===> 2%28p-2%2B4%29%28p-2-2p%29+=+-18,
after direct substitution into the equation.
<===> (p+2)(-p-2) = -9 <===> %28p%2B2%29%5E2+=+9 ===> p+2 = 3, or p+2 = -3
==> p = 1, or p = -5.