Problem 25 - Algebra 1: Concepts and Skills

Question

Solve the inequality. $$ 15+x \geq 7 $$

Step-by-Step Solution

Answer

The solution to the inequality is \(x \geq -8\).

Step 1: Isolate the Variable on One Side

To isolate x on one side, subtract 15 from both sides of the inequality. That leaves: \(x \geq 7 - 15\).

Step 2: Perform the Subtraction

Subtract 15 from 7 to get : \(x \geq -8\)

Key Concepts

Algebraic Inequalities

Understanding algebraic inequalities is crucial for students who want to master algebra. An inequality, like an equation, shows a relationship between expressions. However, unlike equations, inequalities don't indicate equality but rather a range of possible solutions that are 'less than', 'greater than', 'less than or equal to', or 'greater than or equal to' a certain value. The symbols used for inequalities are <, >, \( \leq \), and \( \geq \).

Let's simplify this with an example. Imagine a balance scale where both sides are not always equal but one side can be heavier (greater) or lighter (less) than the other, which relates to how inequalities work. In case of the provided exercise \( 15 + x \geq 7 \), we are comparing the quantity \(15 + x\) to the number 7. The inequality sign \( \geq \) tells us that \(15 + x\) is either greater than or equal to 7. Learning to solve such inequalities is an essential skill in algebra, helping students not just in academics but in everyday decision-making processes where choices fall in a range, like budgeting or measuring.

Isolate the Variable

The goal of isolating the variable is to get the variable we are solving for by itself on one side of the inequality sign. This is a core step in solving both equations and inequalities. To isolate the variable, we use inverse operations–essentially doing the opposite of what is currently being done to the variable.

For instance, if the variable is being added to a number, we subtract that number from both sides. Similarly, if it is being multiplied by a number, we divide both sides by that number. The technique requires careful attention to maintaining the balance of the inequality. In our example \( 15 + x \geq 7 \), the variable x is being added to 15, so we subtract 15 from both sides to isolate x. It's like removing the same weight from both sides of a scale to maintain its balance. As part of this process, we ensure we perform the same operation on both sides of the inequality, so we do not change the relationship between them.

Inequality Solutions

Inequality solutions can differ greatly from solutions to equations because they often represent a set of values rather than a single number. Once a variable is isolated, as in \(x \geq -8\), we can interpret the solution. It tells us that any real number greater than or equal to -8 is a solution to the inequality. In other words, there is not just one answer, but an infinite number of possibilities that satisfy the inequality.

To visualize this, think of a number line. The solution to an inequality would be a section or sections of that line. For our example \(x \geq -8\), we would shade the number line from -8 to positive infinity, including -8 itself because of the 'equal to' part of the symbol (\( \geq \)). It's like having a door partially ajar—the room beyond isn't fully exposed, but you can peek inside. The inequality solution offers just such a peek at all the possible values that work for x.