Basic Practice
Let's solve some basic linear inequalities, then try a few more complicated ones. Just as with linear equations, our goal is to isolate the variable on one side of the inequality sign.
First, what about this: x + 5 > 9. We treat this just like we would if we had x + 5 = 9. We subtract 5 from both sides. Now we have x > 4. On a number line, that would look like this, where x is all numbers larger than, but not equal to, 4.
Note what x + 5 > 9 looks like. Here, the phrase 'x + 5' can be shown as all numbers greater than 9. So all we did was take that 5 away, which shifted our line like this.
Here's another: 18 < 12 + x. Okay, again, get the variable alone. Subtract 12 from both sides and we have 6 < x. We could flip that around to say x > 6. Just remember that if you do that, don't forget to flip the inequality sign! That one looks like this.
Here's one: x - 7 < 1. Let's add 7 to both sides to get x < 8. This graph looks like this. Note that we fill in the circle around the 8 because x isn't just less than 8, it's less than or equal to 8. x could be all these values as well as 8 - no sense making 8 feel left out.
Let's do one more basic one: x + 11 > 14. This time, we subtract 11 from both sides, which gives us x > 3. If we graph that, we get this line. Again, we have a solid circle because x is greater than or equal to 3.
Basic Practice
Let's solve some basic linear inequalities, then try a few more complicated ones. Just as with linear equations, our goal is to isolate the variable on one side of the inequality sign.
First, what about this: x + 5 > 9. We treat this just like we would if we had x + 5 = 9. We subtract 5 from both sides. Now we have x > 4. On a number line, that would look like this, where x is all numbers larger than, but not equal to, 4.
Note what x + 5 > 9 looks like. Here, the phrase 'x + 5' can be shown as all numbers greater than 9. So all we did was take that 5 away, which shifted our line like this.
Here's another: 18 < 12 + x. Okay, again, get the variable alone. Subtract 12 from both sides and we have 6 < x. We could flip that around to say x > 6. Just remember that if you do that, don't forget to flip the inequality sign! That one looks like this.
Here's one: x - 7 < 1. Let's add 7 to both sides to get x < 8. This graph looks like this. Note that we fill in the circle around the 8 because x isn't just less than 8, it's less than or equal to 8. x could be all these values as well as 8 - no sense making 8 feel left out.
Let's do one more basic one: x + 11 > 14. This time, we subtract 11 from both sides, which gives us x > 3. If we graph that, we get this line. Again, we have a solid circle because x is greater than or equal to 3.
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