
MHB Journeyman
#1
February 4th, 2013,
04:10
Here is the question:
Quote:
Show that the function f(x)=(xa)^2*(xb)^2+x takes on the value (a+b)/2 for some value of x.?
Here is a link to the question:
I have posted a link there to this topic so the OP can find my response.

February 4th, 2013 04:10
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MHB Journeyman
#2
February 4th, 2013,
04:14
Thread Author
Hello Karla,
The function $f(x)=(xa)^2(xb)^2+x$ is continuos in $\mathbb{R}$ (polynomical function). Besides, $f(a)=a$ and $f(b)=b$.
But $\dfrac{a+b}{2}$ is the middle point of the segment with endpoints $a$ and $b$ (no matter if $a<b$, $b<a$ or $a=b$) so, $\dfrac{a+b}{2}$ is included between $a$ and $b$. According to the Intermediate Value Theorem, there exists $x\in\mathbb{R}$ such that $f(x)=\dfrac{a+b}{2}$.