Math Problem Statement

For the quadratic function f(x) = x^2 + 4x - 5, determine where the function is increasing, decreasing, and where f(x) > 0 and f(x) < 0.

Solution

Let's analyze the image and the problem.

The quadratic function given is:

f(x)=x2+4x5f(x) = x^2 + 4x - 5

We need to answer a few parts based on this function:

  1. Determine where the function is increasing and decreasing.

    To find where the function is increasing or decreasing, we start by finding the vertex of the quadratic function.

    For a quadratic function f(x)=ax2+bx+cf(x) = ax^2 + bx + c, the x-coordinate of the vertex is given by: x=b2ax = \frac{-b}{2a}

    Here, a=1a = 1 and b=4b = 4, so: x=42(1)=2x = \frac{-4}{2(1)} = -2

    Therefore, the vertex occurs at x=2x = -2. A quadratic function is:

    • Decreasing on the left of the vertex (x<2x < -2)
    • Increasing on the right of the vertex (x>2x > -2)

    Hence, the function is:

    • Decreasing on the interval (,2](-\infty, -2]
    • Increasing on the interval [2,)[-2, \infty)
  2. Determine where f(x)>0f(x) > 0 and where f(x)<0f(x) < 0.

    To find this, we first need to find the roots of the quadratic function by solving f(x)=0f(x) = 0: x2+4x5=0x^2 + 4x - 5 = 0 Factorizing: (x+5)(x1)=0(x + 5)(x - 1) = 0 So, the roots are x=5x = -5 and x=1x = 1.

    Now, analyze the sign of the function:

    • f(x)>0f(x) > 0 when x<5x < -5 or x>1x > 1
    • f(x)<0f(x) < 0 when 5<x<1-5 < x < 1
  3. Based on the intervals, the answer to part (f) is:

    • Option B: f(x)>0f(x) > 0 on (,5)(1,)(-\infty, -5) \cup (1, \infty) and f(x)<0f(x) < 0 on (5,1)(-5, 1).

Let me know if you'd like further details or clarification!

Here are some related questions:

  1. How do you find the axis of symmetry for a quadratic function?
  2. What is the significance of the vertex in a quadratic function?
  3. How can you solve quadratic equations by completing the square?
  4. What is the discriminant of a quadratic equation, and what does it tell us?
  5. How do you graph a quadratic function step by step?

Tip: When analyzing quadratic functions, always start by finding the vertex to determine where the function increases or decreases!

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Vertex of a Parabola
Roots of Quadratic Equation

Formulas

Vertex of a quadratic function: x = -b / 2a
Quadratic equation: f(x) = ax^2 + bx + c
Factoring quadratics

Theorems

Properties of Quadratic Functions
Root Finding in Quadratic Equations

Suitable Grade Level

Grades 9-11