This matches equation (1), so consistent. Use (1): $ z = 4 - 3y $ - Parker Core Knowledge

Understanding the Context

What Is $ z = 4 - 3y $?

At its core, $ z = 4 - 3y $ is a linear equation where:

• $ z $ depends on $ y $,
  
• $ y $ is the independent variable,
  
• $ 4 $ is the $ z $-intercept (value of $ z $ when $ y = 0 $),
  
• $ -3 $ represents the slope (rate of change of $ z $ per unit change in $ y $).

This relationship guarantees that for every real number $ y $ substituted into the equation, there is exactly one unique value of $ z $, maintaining functional consistency.

Why Consistency Matters in Mathematical Equations

Key Insights

Consistency in equations ensures that transformations, substitutions, or calculations yield reliable results. Let’s examine how $ z = 4 - 3y $ supports consistency:

1. Single Output per Input

For each value of $ y $, the equation produces a single, unambiguous value of $ z $. For example:

• If $ y = 0 $, $ z = 4 $.
  
• If $ y = 1 $, $ z = 1 $.
  
• If $ y = -2 $, $ z = 10 $.

This predictability makes the equation a reliable tool in algebra, modeling, and real-world applications.

2. Preservation of Relationships

The equation maintains a consistent proportional relationship between $ y $ and $ z $. The coefficient $ -3 $ ensures a linear decrease in $ z $ as $ y $ increases, which is consistent across all $ y $. This linearity simplifies graphing, simplification, and problem-solving.

3. Easily Manipulable Algebra

Because the equation is linear and well-formed, it can be rearranged or substituted with minimal risk of inconsistency. For instance:

• Solve for $ y $: $ y = rac{4 - z}{3} $
  
• Express in other forms: $ z + 3y = 4 $

Final Thoughts

These transformations preserve truth values, making the equation robust in mathematical reasoning.

Real-World Applications of $ z = 4 - 3y $

This consistent equation isn’t just theoretical—it applies to everyday modeling scenarios where one quantity reliably depends on another:

• Financial modeling: Tracking a discounted price where $ z $ is the final cost and $ y $ is the number of items purchased.
  
• Physics: Describing motion when velocity or displacement evolves linearly over time.
  
• Economics: Predicting revenue based on units sold, assuming constant pricing per unit.

In each case, the consistent behavior of $ z = 4 - 3y $ supports accurate predictions and clear cause-effect relationships.