The simplified expression is x^2 + 9x - 9.

<p>To simplify the expression (2x^2 + 5x - 3) - (x^2 - 4x + 6), we can distribute the negative sign on the second expression and then combine like terms:</p><p>(2x^2 + 5x - 3) - (x^2 - 4x + 6) = 2x^2 + 5x - 3 - x^2 + 4x - 6</p><p>Combining like terms, we get:</p><p>2x^2 - x^2 + 5x + 4x - 3 - 6 = x^2 + 9x - 9</p><p>Therefore, the simplified expression is x^2 + 9x - 9.</p>