5 min read Jun 17, 2024

Exploring the Implicit Function (x^2 + 2)y - x^3 - 3x + 5 = 0

The equation (x^2 + 2)y - x^3 - 3x + 5 = 0 represents an implicit function where y is implicitly defined in terms of x. This means that y is not explicitly solved for and its value is dependent on the value of x. Let's delve into some key aspects of this function:

Understanding the Implicit Nature

The equation doesn't allow us to directly write y as a function of x in the form y = f(x). This is because y is mixed within the equation with x. To understand the relationship, we would need to rearrange the equation or use implicit differentiation to analyze its properties.

Implicit Differentiation

To find the derivative of y with respect to x, we employ implicit differentiation. Here's how it works:

  1. Differentiate both sides of the equation with respect to x.

    • Treat y as a function of x and use the chain rule for terms involving y.
    • Remember that d/dx (x^n) = n*x^(n-1) and d/dx (c) = 0 for any constant 'c'.
  2. Solve the resulting equation for dy/dx. This will give you the derivative of y with respect to x.

Analyzing the Graph

The implicit function defines a curve in the xy-plane. Here are some ways to analyze its graph:

  • Finding the intercepts:
    • x-intercept: Set y = 0 and solve for x.
    • y-intercept: Set x = 0 and solve for y.
  • Determining critical points:
    • Find where the derivative dy/dx is equal to zero or undefined. These points correspond to potential maximum, minimum, or inflection points.
  • Using a graphing tool: Utilize a graphing calculator or online software to visualize the curve. This will provide insights into its shape, behavior, and any special features.

Applications of Implicit Functions

Implicit functions play a vital role in various fields, including:

  • Calculus: Understanding the relationship between variables and their rates of change.
  • Differential equations: Modeling dynamic systems with changing variables.
  • Geometry: Describing curves and surfaces that are not easily expressed as explicit functions.


Let's consider a simplified example:

x^2 + y^2 = 1

This equation represents a circle centered at the origin with a radius of 1. We cannot directly solve for y in terms of x, making it an implicit function. Implicit differentiation can be used to find the slope of the tangent line to the circle at any point.


Implicit functions provide a powerful tool for representing and analyzing relationships between variables that are not explicitly expressed. Understanding implicit differentiation and the techniques for analyzing implicit functions allows us to explore and interpret these complex mathematical relationships.

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