To simplify the expression (a-c)/a - a^2-c^2/ac, we first need to find a common denominator for the fractions.

So, the expression becomes ((a-c)(c))/a - a^2-c^2/ac.

Next, we can simplify further: ac - (a^2c + c^2)/ac.

Now, we can combine like terms by multiplying out the terms in the parenthesis: ac - a^2c - c^2/ac.

Finally, we can combine the terms by finding a common denominator: (ac^2 - a^3c - c^3)/ac.