A/b-b2\a

It looks like you are trying to express a mathematical expression. However, the notation is somewhat unclear, especially with the use of the backslash (\).

If you are expressing the equation: \[ \frac{a}{b} - \frac{b^2}{a} \] This can be simplified. Here are the steps:

1. Find a common denominator for the two fractions, which would be \( ab \).
2. Write the fractions with the common denominator: \[ \frac{a^2}{ab} - \frac{b^3}{ab} \]
3. Combine the fractions: \[ \frac{a^2 - b^3}{ab} \]

The final expression is: \[ \frac{a^2 - b^3}{ab} \]

If you meant something different, please clarify the notation or provide more context!