Math Problem Statement

The function y = x^2 - 4x - 5 increases on which interval?

Solution

The question appears to be asking on which interval the given quadratic function, y=x24x5y = x^2 - 4x - 5, is increasing.

To solve this, let's follow these steps:

  1. Find the derivative of the function y=x24x5y = x^2 - 4x - 5 because the derivative of a function gives us the rate of change of that function. For a quadratic function, it shows whether the function is increasing or decreasing.

    The derivative is: dydx=2x4\frac{dy}{dx} = 2x - 4

  2. Set the derivative equal to zero to find the critical points: 2x4=02x - 4 = 0 Solving for xx: x=2x = 2 This critical point is where the function changes from decreasing to increasing or vice versa.

  3. Analyze the sign of the derivative to determine where the function is increasing:

    • For x>2x > 2, the derivative 2x42x - 4 is positive, meaning the function is increasing.
    • For x<2x < 2, the derivative is negative, meaning the function is decreasing.

Thus, the function increases for x>2x > 2.

Therefore, the correct interval where the function is increasing is (2,+)(2, +\infty), which corresponds to option b.

Do you need further clarification on this solution?

Here are some related questions:

  1. How can you tell if a quadratic function is increasing or decreasing?
  2. What is the significance of the vertex in a quadratic function?
  3. How do you find the critical points of a function?
  4. What happens to a quadratic function as x±x \to \pm\infty?
  5. How can you use the second derivative to determine concavity?

Tip: To quickly determine where a quadratic function is increasing or decreasing, find the derivative and analyze the sign of the derivative around the critical points.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Quadratic Functions

Formulas

y = x^2 - 4x - 5
Derivative of y = 2x - 4

Theorems

First Derivative Test

Suitable Grade Level

Grades 9-12