Solving Square Area, Function Inverses, and Rational Functions Explained

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Question 1: Square Area as a Function of Perimeter

Given Function

  • Area function: A(P) = P2 / 16, where P ≥ 0 (P is the perimeter of the square).
  • Graph is considered for 0 ≤ P ≤ 20.

Part A: Calculate A(20) and A−1(12)

  • Calculate A(20):
    • Substitute P = 20 into A(P): (20)2 / 16 = 400 / 16 = 25.
  • Find inverse A−1(12):
    • Solve A(P) = 12 → P2 / 16 = 12 → P2 = 192 → P ≈ 13.9.
    • Thus, A−1(12) = 13.9.

Part B: Graphing the Inverse Function

  • Draw the line y = x as a reference.
  • Use points from the original function, e.g., (8,4), and switch coordinates to (4,8) for the inverse.
  • Plot these points and sketch the inverse curve.

Part C: Interpretation of Inverse

  • A−1(4) = 8 means a square with area 4 has a perimeter of 8.

Question 2: Function with Square Root

Given Function

  • f(x) = 7 - 4√(x + 5).

Domain and Range

  • Domain: x + 5 ≥ 0 → x ≥ -5.
  • Range: Since the square root is non-negative and multiplied by -4, the maximum value of f(x) is 7 (when x = -5).
  • Therefore, range is y ≤ 7.

Finding Inverse Value

  • Find f−1(2):
    • Set f(x) = 2 → 7 - 4√(x + 5) = 2.
    • Solve for x using calculator or algebra: x ≈ 3.5.

Question 3: Rational Function Analysis

Given Function

  • G(x) = 1 - 3 / (1 - a x).

Part A: Find a given point (2,2)

  • Substitute x=2, G(2)=2:
    • 2 = 1 - 3 / (1 - 2a).
    • Solve for a: a = 2.
  • Updated function: G(x) = 1 - 3 / (1 - 2x).

Part B: Domain and Vertical Asymptote

  • Denominator ≠ 0 → 1 - 2x ≠ 0 → x ≠ 1/2.
  • Vertical asymptote at x = 1/2.

Part C: Intercepts

  • X-intercept (G(x) = 0):
    • 0 = 1 - 3 / (1 - 2x) → solve for x → x = -1.
  • Y-intercept (x=0):
    • G(0) = 1 - 3 / 1 = -2.

Part D: Evaluate G(5) and G−1(5)

  • G(5):
    • G(5) = 1 - 3 / (1 - 2*5) = 1 - 3 / (1 - 10) = 1 - 3 / (-9) = 1 + 1/3 = 4/3 ≈ 1.33.
  • Find G−1(5):
    • Set G(x) = 5 → 1 - 3 / (1 - 2x) = 5.
    • Solve for x → x = 0.25.

Summary

This content demonstrates how to:

  • Calculate function values and inverses for quadratic and square root functions.
  • Graph inverse functions by reflecting points across y = x.
  • Determine domain, range, and vertical asymptotes for rational functions.
  • Find intercepts and solve for unknown parameters using given points.
  • Use calculators effectively to solve equations and verify results.

These techniques are essential for understanding function behavior and solving real-world mathematical problems involving geometry and algebra.

For further reading on related topics, check out these guides:

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