✔ 最佳答案
Hopefully you aren't going with the other answers because none of them are correct.
Let's look at the denominator first.
3x + 1 = 0
3x = -1
x = -1/3
So this is a vertical asymptote. We have to be careful to split this into two cases. You can't just blindly multiply both sides by 3x + 1, because you need to know if it is positive or negative.
Case 1:
3x + 1 is positive (when x > -1/3)
If you multiply both sides by (3x + 1) where it is positive, you don't have to change the sign.
2x - 1 < 2(3x + 1)
2x - 1 < 6x + 2
-4x < 3
Now you are multiplying by a negative, so reverse the sign:
x > -3/4
So you need x > -1/3 and x > -3/4. If you draw this on a number line, you'll see this is equivalent to just saying:
x > -1/3
Case 2:
3x + 1 is negative (x < -1/3)
If you multiply both sides by (3x + 1) where it is negative, you must change the sign.
2x - 1 > 2(3x + 1)
2x - 1 > 6x + 2
-4x > 3
Again change the direction of the sign.
x < -3/4
So now you have:
x < -1/3 and x < -3/4
Again this simplifies to just:
x < -3/4
Combining the cases you have:
x < -3/4
or
x > -1/3
Graphing on a number line it looks like this:
<=== -1 ==( -3/4 ) --- -1/2 --- (-1/3)======= 0 ======>
Edit:
Okay, it's going to be much easier to show if I graph it. Here's the graph of the function in purple. The line y = 2 is shown in green going horizontally. Then there is a vertical asymptote at -1/3. All the places where the function is below the line y = 2 are shown in red (below -3/4 and above -1/3).