Difference between revisions of "2021 Fall AMC 10A Problems/Problem 16"

(Created page with "The graph of <math>f(x) = |\lfloor x \rfloor| - |\lfloor 1 - x \rfloor|</math> is symmetric about which of the following? (Here <math>\lfloor x \rfloor</math> is the greatest...")
 
Line 3: Line 3:
 
<math>\textbf{(A) }</math> the <math>y</math>-axis <math>\qquad \textbf{(B) }</math> the line <math>x = 1</math> <math>\qquad \textbf{(C) }</math> the origin <math>\qquad
 
<math>\textbf{(A) }</math> the <math>y</math>-axis <math>\qquad \textbf{(B) }</math> the line <math>x = 1</math> <math>\qquad \textbf{(C) }</math> the origin <math>\qquad
 
\textbf{(D) }</math> the point <math>\left(\dfrac12, 0\right)</math> <math>\qquad \textbf{(E) }</math> the point <math>(1,0)</math>
 
\textbf{(D) }</math> the point <math>\left(\dfrac12, 0\right)</math> <math>\qquad \textbf{(E) }</math> the point <math>(1,0)</math>
 +
 +
== Solution 1 ==
 +
Since <math>f(1-x)=|\lfloor 1-x \rfloor|-|\lfloor x \rfloor|=-f(x)</math>, <math>f(x)</math> is symmetric about the point <math>\left(\dfrac12, 0\right)</math>
 +
<math>\box{\textbf{(D) } } \text{the point} \left(\dfrac12, 0\right)</math>

Revision as of 12:06, 23 November 2021

The graph of $f(x) = |\lfloor x \rfloor| - |\lfloor 1 - x \rfloor|$ is symmetric about which of the following? (Here $\lfloor x \rfloor$ is the greatest integer not exceeding $x$.)

$\textbf{(A) }$ the $y$-axis $\qquad \textbf{(B) }$ the line $x = 1$ $\qquad \textbf{(C) }$ the origin $\qquad \textbf{(D) }$ the point $\left(\dfrac12, 0\right)$ $\qquad \textbf{(E) }$ the point $(1,0)$

Solution 1

Since $f(1-x)=|\lfloor 1-x \rfloor|-|\lfloor x \rfloor|=-f(x)$, $f(x)$ is symmetric about the point $\left(\dfrac12, 0\right)$ $\box{\textbf{(D) } } \text{the point} \left(\dfrac12, 0\right)$ (Error compiling LaTeX. Unknown error_msg)