QUESTION IMAGE
Question
- find the inverse of the function.
$g(x) = \frac{2x - 8}{4x + 5}$
- write your answer in the form $\frac{ax + b}{cx + d}$, where a, b, c, and d are integers.
$g^{-1}(x) = \square$
Step1: Replace $g(x)$ with $y$
$y = \frac{2x - 8}{4x + 5}$
Step2: Swap $x$ and $y$
$x = \frac{2y - 8}{4y + 5}$
Step3: Cross-multiply to eliminate fraction
$x(4y + 5) = 2y - 8$
$4xy + 5x = 2y - 8$
Step4: Isolate terms with $y$
$4xy - 2y = -8 - 5x$
Step5: Factor out $y$
$y(4x - 2) = -5x - 8$
Step6: Solve for $y$
$y = \frac{-5x - 8}{4x - 2}$
We can factor out $-1$ from numerator and denominator to simplify:
$y = \frac{-(5x + 8)}{2(2x - 1)} = \frac{5x + 8}{-4x + 2}$ (either form is valid, but we present the one with integer coefficients as required)
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$\boldsymbol{\frac{-5x - 8}{4x - 2}}$ (or equivalent $\boldsymbol{\frac{5x + 8}{-4x + 2}}$)