ax2+bx2-ay-bu2-ay2-by =

To simplify the expression \( ax^2 + bx^2 - ay - bu^2 - ay^2 - by \), we can combine like terms.

1. Combine the \( x^2 \) terms: \[ ax^2 + bx^2 = (a + b)x^2 \]

2. Combine the \( y \) terms: \[ -ay - ay^2 - by = -ay^2 - ay - by \]

Putting it all together, the expression simplifies to: \[ (a + b)x^2 - ay^2 - ay - by \]

So the final simplified expression is: \[ (a + b)x^2 - ay^2 - ay - by \]