Difference between revisions of "1983 AIME Problems/Problem 2"

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== Solution ==
 
== Solution ==
It is best to get rid of the [[absolute value]] first.  
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It is best to get rid of the [[absolute value]]s first.  
  
 
Under the given circumstances, we notice that <math>|x-p|=x-p</math>, <math>|x-15|=15-x</math>, and <math>|x-p-15|=15+p-x</math>.
 
Under the given circumstances, we notice that <math>|x-p|=x-p</math>, <math>|x-15|=15-x</math>, and <math>|x-p-15|=15+p-x</math>.
  
Adding these together, we find that the sum is equal to <math>30-x</math>, of which the minimum value is attained when <math>x=\boxed{015}</math>.
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Adding these together, we find that the sum is equal to <math>30-x</math>, which attains its minimum value (on the given interval <math>p \leq x \leq 15</math>) when <math>x=\boxed{015}</math>.
 
 
Also note the lowest value occurs when <math>x=p=15</math> because this make the first two requirements <math>0</math>. It is easy then to check that 15 is the minimum value.
 
  
 
== See Also ==
 
== See Also ==

Revision as of 19:04, 15 February 2019

Problem

Let $f(x)=|x-p|+|x-15|+|x-p-15|$, where $0 < p < 15$. Determine the minimum value taken by $f(x)$ for $x$ in the interval $p \leq x\leq15$.

Solution

It is best to get rid of the absolute values first.

Under the given circumstances, we notice that $|x-p|=x-p$, $|x-15|=15-x$, and $|x-p-15|=15+p-x$.

Adding these together, we find that the sum is equal to $30-x$, which attains its minimum value (on the given interval $p \leq x \leq 15$) when $x=\boxed{015}$.

See Also

1983 AIME (ProblemsAnswer KeyResources)
Preceded by
Problem 1
Followed by
Problem 3
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All AIME Problems and Solutions