Difference between revisions of "1969 AHSME Problems/Problem 14"

m (See also)
(Solution to Problem 14)
 
Line 10: Line 10:
  
 
== Solution ==
 
== Solution ==
<math>\fbox{A}</math>
+
Factor the [[difference of squares]].
 +
<cmath>\frac{(x+2)(x-2)}{(x+1)(x-1)}>0</cmath>
 +
Note that the graph intersects the x-axis at when <math>x = \pm2</math> or <math>x \pm 1</math>, so check the sign of the result to see if it is positive.  After testing, <math>x<-2</math> or <math>-1<x<1</math> or <math>x>2</math>, so the answer is <math>\boxed{\textbf{(A)}}</math>.
  
 
== See also ==
 
== See also ==

Latest revision as of 03:35, 7 June 2018

Problem

The complete set of $x$-values satisfying the inequality $\frac{x^2-4}{x^2-1}>0$ is the set of all $x$ such that:

$\text{(A) } x>2 \text{ or } x<-2 \text{ or} -1<x<1\quad  \text{(B) } x>2 \text{ or } x<-2\quad \\ \text{(C) } x>1 \text{ or } x<-2\qquad\qquad\qquad\quad \text{(D) } x>1 \text{ or } x<-1\quad \\ \text{(E) } x \text{ is any real number except 1 or -1}$

Solution

Factor the difference of squares. \[\frac{(x+2)(x-2)}{(x+1)(x-1)}>0\] Note that the graph intersects the x-axis at when $x = \pm2$ or $x \pm 1$, so check the sign of the result to see if it is positive. After testing, $x<-2$ or $-1<x<1$ or $x>2$, so the answer is $\boxed{\textbf{(A)}}$.

See also

1969 AHSC (ProblemsAnswer KeyResources)
Preceded by
Problem 13
Followed by
Problem 15
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
All AHSME Problems and Solutions

The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. AMC logo.png