81
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To write the expression with positive exponents only, we need to convert the negative exponent to a positive exponent. The rule for this is:
Applying this rule to 1/9 with a negative 2 exponent:
- 1 / 9⁻² = 1 / (1 / 9²) = 1 * 9² = 1 * 81 = 81
So, the simplified expression is 81.