Evaluate
$$ \lim_{x\to \infty} \left( \frac{a^x -1}{x(a-1)} \right)^{1\slash x},$$
where $a>0$ and $a\ne 1.$
To evaluate the limit 
\[ \lim_{x\to \infty} \left( \frac{a^x -1}{x(a-1)} \right)^{1/x}, \]
where \( a > 0 \) and \( a \ne 1 \), we will consider two cases: \( a > 1 \) and \( 0 < a < 1 \).

### Case 1: \( a > 1 \)

1. Let \( L = \lim_{x\to \infty} \left( \frac{a^x -1}{x(a-1)} \right)^{1/x} \). Taking the natural logarithm of both sides, we get:
   \[ \ln L = \lim_{x\to \infty} \frac{\ln \left( \frac{a^x -1}{x(a-1)} \right)}{x}. \]

2. Simplify the logarithm inside the limit:
   \[ \ln L = \lim_{x\to \infty} \frac{\ln (a^x - 1) - \ln x - \ln (a-1)}{x}. \]

3. Apply L'Hôpital's Rule to evaluate the limit. First, differentiate the numerator and the denominator with respect to \( x \):
   \[ \ln L = \lim_{x\to \infty} \frac{\frac{d}{dx} \left( \ln (a^x - 1) - \ln x - \ln (a-1) \right)}{\frac{d}{dx} x}. \]

4. The derivatives are:
   \[ \frac{d}{dx} \ln (a^x - 1) = \frac{a^x \ln a}{a^x - 1}, \quad \frac{d}{dx} \ln x = \frac{1}{x}, \quad \frac{d}{dx} \ln (a-1) = 0. \]

5. Substitute these derivatives into the limit:
   \[ \ln L = \lim_{x\to \infty} \left( \frac{a^x \ln a}{a^x - 1} - \frac{1}{x} \right). \]

6. As \( x \to \infty \), \( a^x \) grows much faster than 1, so \( \frac{a^x}{a^x - 1} \to 1 \). Therefore:
   \[ \ln L = \ln a \lim_{x\to \infty} \left( \frac{a^x}{a^x - 1} \right) = \ln a. \]

7. Exponentiate both sides to solve for \( L \):
   \[ L = e^{\ln a} = a. \]

### Case 2: \( 0 < a < 1 \)

1. Let \( L = \lim_{x\to \infty} \left( \frac{a^x -1}{x(a-1)} \right)^{1/x} \). Taking the natural logarithm of both sides, we get:
   \[ \ln L = \lim_{x\to \infty} \frac{\ln \left( \frac{1 - a^x}{x(1-a)} \right)}{x}. \]

2. Simplify the logarithm inside the limit:
   \[ \ln L = \lim_{x\to \infty} \frac{\ln (1 - a^x) - \ln x - \ln (1-a)}{x}. \]

3. Apply L'Hôpital's Rule to evaluate the limit. First, differentiate the numerator and the denominator with respect to \( x \):
   \[ \ln L = \lim_{x\to \infty} \frac{\frac{d}{dx} \left( \ln (1 - a^x) - \ln x - \ln (1-a) \right)}{\frac{d}{dx} x}. \]

4. The derivatives are:
   \[ \frac{d}{dx} \ln (1 - a^x) = \frac{-a^x \ln a}{1 - a^x}, \quad \frac{d}{dx} \ln x = \frac{1}{x}, \quad \frac{d}{dx} \ln (1-a) = 0. \]

5. Substitute these derivatives into the limit:
   \[ \ln L = \lim_{x\to \infty} \left( \frac{-a^x \ln a}{1 - a^x} - \frac{1}{x} \right). \]

6. As \( x \to \infty \), \( a^x \to 0 \), so \( \frac{a^x}{1 - a^x} \to 0 \). Therefore:
   \[ \ln L = \ln a \lim_{x\to \infty} \left( \frac{a^x}{1 - a^x} \right) = 0. \]

7. Exponentiate both sides to solve for \( L \):
   \[ L = e^0 = 1. \]

The final answer is \( \boxed{a} \) if \( a > 1 \) and \( \boxed{1} \) if \( 0 < a < 1 \).