McGraw Hill Glencoe Algebra 1, 2012
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McGraw Hill Glencoe Algebra 1, 2012 View details
5. Inequalities Involving Absolute Value
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Exercise 21 Page 314

Create an or compound inequality because the absolute value is greater than or equal to the given value.

Solution Set: { n | n≤- 5 14 or n≥ 3 34}
Graph:

Practice makes perfect
We are asked to find and graph the solution set for all possible values of n in the given inequality. |4n+3|≥ 18 To do this, we will create a compound inequality by removing the absolute value. In this case, and since 4n+3 can be written as 4n-(- 3), the solution set contains the numbers that make the distance between 4n and - 3 greater than or equal to 18 in the positive direction or in the negative direction. 4n+3 ≥ 18 or 4n+3≤ - 18

Let's isolate n in both of these cases before graphing the solution set.

Case 1

4n+3≥ 18
4n≥ 15
n≥15/4
â–Ľ
Write fraction as a mixed number
n≥12+3/4
n≥12/4+3/4
n≥ 3+3/4
n≥3 34
This inequality tells us that all values greater than or equal to 3 34 will satisfy the inequality.

Case 2

4n+3≤- 18
4n≤- 21
n≤- 21/4
n≤-21/4
â–Ľ
Write fraction as a mixed number
n≤-20+1/4
n≤-(20/4+1/4)
n≤-(5+1/4)
n≤-(5 14)
n≤- 5 14
This inequality tells us that all values less than or equal to - 5 14 will satisfy the inequality.

Solution Set

The solution to this type of compound inequality is the combination of the solution sets. First Solution Set:& n≥ 3 34 [0.5em] Second Solution Set:& n≤ - 5 14 [0.5em] Combined Solution Set:& n≤ - 5 14 or n≥ 3 34

Graph

The graph of this inequality includes all values less than or equal to - 5 14 or greater than or equal to 3 34. We show this by keeping the endpoints closed.