Math Problem Statement

Use the functions f(x) = 1/x - 3 and g(x) = x^3 to find the indicated value or function for exercises 83-88. Then, use the functions f(x) = x + 4 and g(x) = 2x - 5 for exercises 89-92.

Solution

Let's go through the problem step by step, starting with the relevant functions:

  • f(x)=1x3f(x) = \frac{1}{x} - 3
  • g(x)=x3g(x) = x^3

Solving Exercises 83-88

83. (f1g1)(1)(f^{-1} \circ g^{-1})(1)
This means we need to find f1(g1(1))f^{-1}(g^{-1}(1)). We'll first find the inverse functions of f(x)f(x) and g(x)g(x), then evaluate the composition.

  1. Find the inverse of g(x)=x3g(x) = x^3: g1(x)=x3g^{-1}(x) = \sqrt[3]{x}

  2. Find the inverse of f(x)=1x3f(x) = \frac{1}{x} - 3: Set y=1x3y = \frac{1}{x} - 3, then solve for xx: y+3=1xy + 3 = \frac{1}{x} x=1y+3x = \frac{1}{y + 3} So, f1(x)=1x+3f^{-1}(x) = \frac{1}{x + 3}.

  3. Now, compute g1(1)=13=1g^{-1}(1) = \sqrt[3]{1} = 1.

  4. Plug this into f1f^{-1}: f1(1)=11+3=14f^{-1}(1) = \frac{1}{1 + 3} = \frac{1}{4}

Thus, (f1g1)(1)=14(f^{-1} \circ g^{-1})(1) = \frac{1}{4}.


84. (g1f1)(3)(g^{-1} \circ f^{-1})(-3)

  1. From earlier, we know f1(x)=1x+3f^{-1}(x) = \frac{1}{x + 3}.
  2. Compute f1(3)=13+3=undefinedf^{-1}(-3) = \frac{1}{-3 + 3} = \text{undefined} (division by 0).

So, (g1f1)(3)(g^{-1} \circ f^{-1})(-3) is undefined.


85. (f1f)(6)(f^{-1} \circ f)(6)
Since f1(f(x))=xf^{-1}(f(x)) = x, this simplifies to: (f1f)(6)=6(f^{-1} \circ f)(6) = 6


86. (g1g1)(4)(g^{-1} \circ g^{-1})(-4)
First, compute g1(4)=43g^{-1}(-4) = \sqrt[3]{-4}. There's no simple cube root of 4-4, so we leave this as 43\sqrt[3]{-4}.

Next, compute g1(43)g^{-1}(\sqrt[3]{-4}), which would be the cube root of 43\sqrt[3]{-4}, or (4)1/9(-4)^{1/9}, an irrational number. The exact value is complex, but it's approximately 1.1487-1.1487.


87. (fg)1(f \circ g)^{-1}
This asks for the inverse of the composition. First, find f(g(x))f(g(x)): f(g(x))=f(x3)=1x33f(g(x)) = f(x^3) = \frac{1}{x^3} - 3 To find the inverse of f(g(x))f(g(x)), let y=1x33y = \frac{1}{x^3} - 3, then solve for xx. This would be a more involved process requiring algebraic manipulation.


Moving to Exercises 89-92 (using new functions):

  • f(x)=x+4f(x) = x + 4
  • g(x)=2x5g(x) = 2x - 5

89. g1f1g^{-1} \circ f^{-1}
This requires first finding the inverses of both functions and then composing them.

Would you like me to continue solving the remaining exercises in detail or expand on one of these steps?


5 Related Questions:

  1. How do you find the inverse of a general function?
  2. Why is f1(x)=1x+3f^{-1}(x) = \frac{1}{x+3} the inverse of f(x)f(x)?
  3. What happens if a function is not invertible at a certain point (e.g., x=3x = -3)?
  4. Can the cube root of a negative number be calculated, and how?
  5. How does function composition affect the domain and range of the resulting function?

Tip:

When finding the inverse of a composition of functions, try breaking the problem down by solving the innermost function's inverse first and then moving outward.

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Math Problem Analysis

Mathematical Concepts

Inverse Functions
Function Composition

Formulas

f(x) = 1/x - 3
g(x) = x^3
f(x) = x + 4
g(x) = 2x - 5
Inverse function formula: f^(-1)(x)

Theorems

Inverse Function Theorem
Composition of Functions

Suitable Grade Level

Grades 11-12