Chapter 8: Problem 8
Solve each inequality and check your solution. Then graph the solution on a number line. $$-2(k+1) \geq 16$$
Short Answer
Expert verified
The solution is \(k \leq -9\).
Step by step solution
01
Distribute the Coefficient
First, distribute the -2 to both terms inside the parenthesis. This means you multiply -2 by both \(k\) and 1. So we have:\[-2 \cdot (k+1) = -2k - 2\] This simplifies our inequality to:\[-2k - 2 \geq 16\]
02
Isolate the Variable Term
Next, add 2 to both sides of the inequality to move the constant term:\[-2k - 2 + 2 \geq 16 + 2\]This simplifies to:\[-2k \geq 18\]
03
Solve for the Variable
To solve for \(k\), divide both sides by -2, remembering to flip the inequality sign:\[\frac{-2k}{-2} \leq \frac{18}{-2}\]Resulting in:\[k \leq -9\]
04
Check the Solution
To check, choose a value less than or equal to -9 and substitute back into the original inequality. Use \(k = -10\) as an example:\[-2(-10 + 1) = -2(-9) = 18\]Since \(18 \geq 16\), the solution \(k \leq -9\) is confirmed.
05
Graph the Solution
Draw a number line, mark the point -9, and shade all values to the left, including -9, to represent \(k \leq -9\). Use a closed circle on -9 to indicate that it is part of the solution.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Distributive Property
In mathematics, the distributive property is a fundamental concept that allows you to simplify expressions by distributing a factor across terms inside parentheses. In our exercise, the expression \(-2(k+1)\) requires using the distributive property.
- Multiply \(-2\) by each term inside the parentheses: \(k\) and \(1\).
- This gives us: \(-2 \cdot k = -2k\) and \(-2 \cdot 1 = -2\).
- Combine these results to rewrite the expression as \(-2k - 2\).
Number Line
A number line is a visual representation of numbers laid out on a straight line. For inequalities, it helps illustrate the range of possible solutions.
- After solving the inequality \(k \leq -9\), the number line is used to graph the solution.
- Mark the point \(-9\) on the line with a closed circle, since \(-9\) is included in the solution set.
- Shade the entire region to the left of \(-9\), indicating all values less than or equal to \(-9\).
Checking Solutions
Checking solutions is a crucial step when solving inequalities to ensure correctness. It involves substituting a possible solution back into the original inequality to verify its validity.
- For \(k \leq -9\), choose a test value, such as \(k = -10\).
- Substitute \(-10\) into the original inequality: \(-2(-10 + 1)\).
- Simplify to find \(18\), which satisfies the condition \(18 \geq 16\).
Solving Inequalities
Solving inequalities involves finding the set of values that satisfy a given inequality. It is similar to solving equations, but requires special attention to how the inequality behaves, especially when multiplying or dividing by negative numbers.
- Firstly, use methods such as the distributive property to simplify the inequality.
- Isolate the variable by moving all terms involving the variable to one side and constants to the other.
- In this example, adding 2 to both sides gives \(-2k \geq 18\). Divide by \(-2\), and remember to flip the inequality sign, resulting in \(k \leq -9\).