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Question
Determine algebraically whether k(x) and j(x) are inverse functions. True or False.

k(x)=7−x4−2x and j(x)=4x+62x−1

(1 point)
Responses

True
True

False

1 answer

To determine whether \( k(x) \) and \( j(x) \) are inverse functions, we need to check if \( k(j(x)) = x \) and \( j(k(x)) = x \).

  1. Finding \( k(j(x)) \):

    • Substitute \( j(x) = 4x + 6 \) into \( k(x) \): \[ k(j(x)) = k(4x + 6) = 7 - \frac{(4x + 6)}{4} - 2(4x + 6) \]

    Simplifying this:

    • First calculate \( \frac{(4x + 6)}{4} = x + \frac{3}{2} \).
    • Now plug this back into \( k \): \[ k(j(x)) = 7 - (x + \frac{3}{2}) - 2(4x + 6) \] \[ = 7 - x - \frac{3}{2} - (8x + 12) \] \[ = 7 - x - 8x - 12 - \frac{3}{2} = 7 - 12 - \frac{3}{2} - 9x \] The simplification show that it does not equal \( x \).
  2. Finding \( j(k(x)) \):

    • Substitute \( k(x) = 7 - \frac{x}{4 - 2x} \) into \( j(x) \): \[ j(k(x)) = j(7 - \frac{x}{4 - 2x}) = 4(7 - \frac{x}{4 - 2x}) + 6 \]
    • Simplifying, we will arrive at a complex polynomial, not guaranteed to be equal to \( x \).

Since we can derive from above that \( k(j(x)) \neq x \) for at least one substitution, we can conclude that:

The functions \( k(x) \) and \( j(x) \) are not inverse functions.

Thus, the correct answer is: False.