SOLUTION: The absolute value of {{{ 1- 1/x }}} is less than and equal to 3. Solve the inequality, express your answer in interval notation.

Algebra ->  Inequalities -> SOLUTION: The absolute value of {{{ 1- 1/x }}} is less than and equal to 3. Solve the inequality, express your answer in interval notation.      Log On


   



Question 289387: The absolute value of +1-+1%2Fx+ is less than and equal to 3. Solve the inequality, express your answer in interval notation.
Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!

abs%281-1%2Fx%29%3C=3

We find the critical values by solving the boundary equation:

abs%281-1%2Fx%29=3

Which breaks into these two equations:

1-1%2Fx=3  or 1-1%2Fx=-3

x-1=3x   or x-1=-3x

-2x=1    or 4x=1

x=-1%2F2   or x=1%2F4

We also have a third critical value x=0 because
that is what we get when we set the denominator
in the original problem = 0.  

So we put those points on a number line

----------------o----o--o------------------
-2       -1   -1/2   0 1/4      1         2

We test a value left of -1/2, say -1, in the
original inequality:

abs%281-1%2Fx%29%3C=3
abs%281-1%2F%28-1%29%29%3C=3
abs%281%2B1%29%3C=3
abs%282%29%3C=3

That's true, so we shade the region left of -1/2

<================o----o--o------------------
 -2       -1   -1/2   0 1/4      1         2

We test a value between -1/2 and 0, say -.2 in the
original inequality:

abs%281-1%2Fx%29%3C=3
abs%281-1%2F%28-.2%29%29%3C=3
abs%281%2B5%29%3C=3
abs%286%29%3C=3
6%3C=3


That's false, so we DO NOT shade the region between
-1/2 and 0

We test a value between 0 and 1/4, say .2 in the
original inequality:

abs%281-1%2Fx%29%3C=3
abs%281-1%2F%28.2%29%29%3C=3
abs%281-5%29%3C=3
abs%28-4%29%3C=3
4%3C=3

That's false, so we DO NOT shade the region between
0 and 1/4.

We test a value right of 1/4, say 1, in the
original inequality:

abs%281-1%2Fx%29%3C=3
abs%281-1%2F%281%29%29%3C=3
abs%281-1%29%3C=3
abs%280%29%3C=3

abs%281-1%2F%28-1%2F2%29%29%3C=3
abs%281%2B2%29%3C=3
abs%283%29%3C=3
3%3C=3

That's true so we shade -1/2

<================@----o--o=================>
 -2       -1   -1/2   0 1/4      1         2

Now we test the endpoint 1/4

abs%281-1%2Fx%29%3C=3
abs%281-1%2F%281%2F4%29%29%3C=3
abs%281-4%29%3C=3
abs%28-3%29%3C=3
3%3C=3

That's true so we shade 1/4

<================@----o--@=================>
 -2       -1   -1/2   0 1/4      1         2

So the solution set is:

%22%28%22-infinity%22%2C%22-1%2F2%22%5D%22U%22%5B%221%2F4%22%2C%22infinity%22%29%22

Edwin