a:a=1

The equation \( a : a = 1 \) represents the proportion of \( a \) to itself. Since any non-zero number divided by itself equals 1, this is true for all \( a \neq 0 \).

To elaborate:

\[ \frac{a}{a} = 1 \quad \text{for } a \neq 0 \]

If \( a = 0 \), the expression is undefined because division by zero is not permitted.

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