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April 14th, 2014, 09:54 AM  #1 
Newbie Joined: Apr 2014 From: The Netherlands Posts: 7 Thanks: 2  Line intersections
Edit: Oops! This is in the wrong section, maybe it better fits in precalc/calc. I'll just walk through the question as it is asked in the book I'm studying. Excuse me for grammar errors. Suppose we have the following function: a) Calculate the extreme value of f(x) and give the range of f(x) So, we simply need to calculate f'(x) and set it to zero. Because I did answer a) correctly, I'll simply just get continue with posting f'(x) instead of deriving it step by step. Now we need to set it to zero. Which will yield: Putting these values in the original equation will result in the extreme values: (minimum) and (maximum). The range of f(x) will thus be b) Calculate (algebraically) for which a the equation f(x) = ax has exactly one unique solution. So, from this point on I have absolutely no idea what to do. Can anyone help me out? c) Calculate (algebraically) for which p the equation f(x) = 2/3x + p has three solutions. I thought that if I could get some help on b I could try and solve b and c in this topic :^). Last edited by jyrdo; April 14th, 2014 at 10:01 AM. Reason: Wrong section 
April 14th, 2014, 11:47 AM  #2 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,664 Thanks: 2644 Math Focus: Mainly analysis and algebra 
You need to find where $f(x) = ax$. That is the same as finding where $$g(x) = f(x)  ax = 0$$ So, try solving that for $x$, and see what value of $a$ gives a single (possibly repeated) solution in the real numbers. 
April 14th, 2014, 12:13 PM  #3  
Newbie Joined: Apr 2014 From: The Netherlands Posts: 7 Thanks: 2  Quote:
I get that I have to find where $f(x) = ax$, but I don't think I'll find it the way I'm trying right now.  
April 15th, 2014, 03:04 AM  #4 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,948 Thanks: 1139 Math Focus: Elementary mathematics and beyond 
$\displaystyle \frac{6x}{x^2+5}=ax$ $\displaystyle 6=ax^2+5a$ $\displaystyle ax^2=65a=0\Rightarrow a=\frac65$ 

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intersections, line 
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