Math Problem Statement

Use the functions f left parenthesis x right parenthesis equals x squared minus 4 and g left parenthesis x right parenthesis equals x plus 8 to answer parts​ (a)-(g). ​(a) Solve f left parenthesis x right parenthesis equals 0. ​(d) Solve f left parenthesis x right parenthesis greater than 0. ​(g) Solve f left parenthesis x right parenthesis greater than or equals 1. ​(b) Solve g left parenthesis x right parenthesis equals 0. ​(e) Solve g left parenthesis x right parenthesis less than or equals 0. ​(c) Solve f left parenthesis x right parenthesis equals g left parenthesis x right parenthesis. ​(f) Solve f left parenthesis x right parenthesis greater than g left parenthesis x right parenthesis.

Solution

To answer these parts using the given functions f(x)=x24f(x) = x^2 - 4 and g(x)=x+8g(x) = x + 8, let’s break down each one step by step.

(a) Solve f(x)=0f(x) = 0

We are asked to solve x24=0x^2 - 4 = 0.

  1. Factor the quadratic equation: (x2)(x+2)=0(x - 2)(x + 2) = 0
  2. Set each factor equal to zero: x2=0orx+2=0x - 2 = 0 \quad \text{or} \quad x + 2 = 0 x=2orx=2x = 2 \quad \text{or} \quad x = -2 Thus, the solutions are x=2x = 2 and x=2x = -2.

(d) Solve f(x)>0f(x) > 0

We are asked to solve x24>0x^2 - 4 > 0.

  1. Factor the inequality: (x2)(x+2)>0(x - 2)(x + 2) > 0
  2. The critical points are x=2x = 2 and x=2x = -2. We test intervals:
    • For x<2x < -2, choose x=3x = -3: (3)24=94=5(-3)^2 - 4 = 9 - 4 = 5, which is positive.
    • For 2<x<2-2 < x < 2, choose x=0x = 0: (0)24=4(0)^2 - 4 = -4, which is negative.
    • For x>2x > 2, choose x=3x = 3: (3)24=94=5(3)^2 - 4 = 9 - 4 = 5, which is positive.

Therefore, f(x)>0f(x) > 0 when x<2x < -2 or x>2x > 2. In interval notation, the solution is: x(,2)(2,)x \in (-\infty, -2) \cup (2, \infty)

(g) Solve f(x)1f(x) \geq 1

We are asked to solve x241x^2 - 4 \geq 1.

  1. Add 4 to both sides: x25x^2 \geq 5
  2. Solve for xx: x5orx5x \geq \sqrt{5} \quad \text{or} \quad x \leq -\sqrt{5} Thus, the solution is x(,5][5,)x \in (-\infty, -\sqrt{5}] \cup [\sqrt{5}, \infty).

(b) Solve g(x)=0g(x) = 0

We are asked to solve x+8=0x + 8 = 0.

  1. Subtract 8 from both sides: x=8x = -8 Thus, the solution is x=8x = -8.

(e) Solve g(x)0g(x) \leq 0

We are asked to solve x+80x + 8 \leq 0.

  1. Subtract 8 from both sides: x8x \leq -8 Thus, the solution is x8x \leq -8.

(c) Solve f(x)=g(x)f(x) = g(x)

We are asked to solve x24=x+8x^2 - 4 = x + 8.

  1. Rearrange the equation: x2x12=0x^2 - x - 12 = 0
  2. Factor the quadratic equation: (x4)(x+3)=0(x - 4)(x + 3) = 0
  3. Set each factor equal to zero: x=4orx=3x = 4 \quad \text{or} \quad x = -3 Thus, the solutions are x=4x = 4 and x=3x = -3.

(f) Solve f(x)>g(x)f(x) > g(x)

We are asked to solve x24>x+8x^2 - 4 > x + 8.

  1. Rearrange the inequality: x2x12>0x^2 - x - 12 > 0
  2. Factor the quadratic inequality: (x4)(x+3)>0(x - 4)(x + 3) > 0
  3. Test intervals:
    • For x<3x < -3, choose x=4x = -4: (44)(4+3)=(8)(1)>0(-4 - 4)(-4 + 3) = (-8)(-1) > 0.
    • For 3<x<4-3 < x < 4, choose x=0x = 0: (04)(0+3)=(4)(3)<0(0 - 4)(0 + 3) = (-4)(3) < 0.
    • For x>4x > 4, choose x=5x = 5: (54)(5+3)=(1)(8)>0(5 - 4)(5 + 3) = (1)(8) > 0.

Thus, f(x)>g(x)f(x) > g(x) when x<3x < -3 or x>4x > 4. In interval notation, the solution is: x(,3)(4,)x \in (-\infty, -3) \cup (4, \infty)


Would you like more details on any part, or do you have any questions? Here are some related problems to explore:

  1. Solve f(x)=1f(x) = 1 for f(x)=x24f(x) = x^2 - 4.
  2. Find the range of g(x)=x+8g(x) = x + 8.
  3. Solve f(x)0f(x) \leq 0.
  4. Determine when f(x)=g(x)+5f(x) = g(x) + 5.
  5. Analyze the graph of f(x)f(x) and g(x)g(x) to visualize the solutions.

Tip: When solving inequalities involving quadratics, always test intervals based on critical points found by solving the equation first.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Inequalities

Formulas

f(x) = x^2 - 4
g(x) = x + 8
Quadratic factorization: (x - r)(x + r) = 0

Theorems

Quadratic Factorization Theorem
Properties of Inequalities

Suitable Grade Level

Grades 8-10