SOLUTION: Solve the inequality. Express your answer using set notation or interval notation. Graph the solution set. 0 < (3x + 6)^(-1) < 1/3

Algebra ->  Inequalities -> SOLUTION: Solve the inequality. Express your answer using set notation or interval notation. Graph the solution set. 0 < (3x + 6)^(-1) < 1/3       Log On


   



Question 1207722: Solve the inequality. Express your answer using set notation or interval notation. Graph the solution set.

0 < (3x + 6)^(-1) < 1/3

Answer by ikleyn(52835) About Me  (Show Source):
You can put this solution on YOUR website!
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Solve the inequality. Express your answer using set notation or interval notation. Graph the solution set.
0 < (3x + 6)^(-1) < 1/3
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Your starting inequality is

    0 < 1%2F%283x%2B6%29 < 1%2F3.    (1)


Left part of this inequality,  0 < 1%2F%283x%2B6%29,  means that the denominator is positive

    3x + 6 > 0    (otherwise,  1%2F%283x%2B6%29  would be negative).


It implies  3x > - 6,  x > -6%2F3 = -2.    (2)


Right part of this inequality is

    1%2F%283x%2B6%29 < 1%2F3.


Assuming that 3x+6 is positive, we can multiply both sides by 3x+6 without flipping the inequality sign.
By doing it, we get

    1 < %283x%2B6%29%2F3,

or, equivalently,

    1 < x+2.

It implies 

    x > -1.    (3)


So, we have two inequalities,  (2) and (3).


Therefore, the final answer is  the intersection of these two sets,  x > -1.


In the interval form, the solution set is  (-1,infinity).


This is a graph


   ----|--------|--------(========|========|========|======>
       -3       -2       -1       0        1        2     x

Solved.