Math Problem Statement

Find the derivative of f(g(x)) at x = -2 and g(x^3) at x = -2 using the given graph.

Solution

Let’s solve the given problems step by step:


1. Find ddx(f(g(x)))x=2\frac{d}{dx} \big(f(g(x))\big) \big|_{x = -2}

This requires the chain rule, which states: ddx(f(g(x)))=f(g(x))g(x)\frac{d}{dx} \big(f(g(x))\big) = f'(g(x)) \cdot g'(x)

Steps:

  1. Find g(2)g(-2): From the graph, when x=2x = -2, g(x)=0g(x) = 0.

  2. Find g(x)g'(x) at x=2x = -2: The derivative of g(x)g(x) at x=2x = -2 is the slope of the line segment of g(x)g(x) near x=2x = -2.
    Observing the graph:

    • The line segment from x=4x = -4 to x=0x = 0 has a slope: g(x)=3(3)0(4)=64=32g'(x) = \frac{3 - (-3)}{0 - (-4)} = \frac{6}{4} = \frac{3}{2} So, g(2)=32g'(-2) = \frac{3}{2}.
  3. Find f(x)f'(x) at g(x)=0g(x) = 0: From the graph, when x=0x = 0, f(x)f(x) is on a horizontal segment, so: f(0)=1(since the slope of the segment is 1).f'(0) = 1 \quad (\text{since the slope of the segment is } 1).

  4. Combine using the chain rule: ddx(f(g(x)))x=2=f(g(2))g(2)=f(0)32=132=32\frac{d}{dx} \big(f(g(x))\big) \big|_{x = -2} = f'(g(-2)) \cdot g'(-2) = f'(0) \cdot \frac{3}{2} = 1 \cdot \frac{3}{2} = \frac{3}{2}


2. Find ddx(g(x3))x=2\frac{d}{dx} \big(g(x^3)\big) \big|_{x = -2}

This requires the chain rule, which states: ddx(g(x3))=g(x3)ddx(x3)\frac{d}{dx} \big(g(x^3)\big) = g'(x^3) \cdot \frac{d}{dx}(x^3)

Steps:

  1. Find x3x^3 at x=2x = -2: x3=(2)3=8x^3 = (-2)^3 = -8

  2. Find g(8)g'(-8): From the graph, when x=8x = -8, g(x)g(x) is on a line segment with slope: g(x)=0(4)6(8)=42=2g'(x) = \frac{0 - (-4)}{-6 - (-8)} = \frac{4}{2} = 2 So, g(8)=2g'(-8) = 2.

  3. Find ddx(x3)\frac{d}{dx}(x^3): ddx(x3)=3x2\frac{d}{dx}(x^3) = 3x^2

  4. Combine using the chain rule: ddx(g(x3))x=2=g(x3)3x2=g(8)3(2)2=234=24\frac{d}{dx} \big(g(x^3)\big) \big|_{x = -2} = g'(x^3) \cdot 3x^2 = g'(-8) \cdot 3(-2)^2 = 2 \cdot 3 \cdot 4 = 24


Final Answers:

  1. ddx(f(g(x)))x=2=32\frac{d}{dx} \big(f(g(x))\big) \big|_{x = -2} = \frac{3}{2}
  2. ddx(g(x3))x=2=24\frac{d}{dx} \big(g(x^3)\big) \big|_{x = -2} = 24

Would you like detailed explanations for any specific part?
Here are 5 related questions to practice:

  1. What is the chain rule, and how does it apply to composite functions?
  2. How do you compute slopes of piecewise linear functions from graphs?
  3. How would you solve ddx(f(g(x2)))\frac{d}{dx} \big(f(g(x^2))\big) at a given xx?
  4. What is the geometric significance of derivatives on graphs?
  5. How does g(x)g(x) behave as xx \to \infty based on the graph?

Tip: Always double-check slopes for accuracy by picking two distinct points on the graph.

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Math Problem Analysis

Mathematical Concepts

Differentiation
Chain Rule
Piecewise Functions

Formulas

d/dx(f(g(x))) = f'(g(x)) * g'(x)
d/dx(g(x^3)) = g'(x^3) * d/dx(x^3)

Theorems

Chain Rule of Differentiation

Suitable Grade Level

Grades 10-12