Altitude to the hypotenuse of a 7–24–25 triangle

In right-angled triangle \(ABC\), \(\angle ACB=90^\circ\), \(AC=24\) cm and \(BC=7\) cm. Point \(D\) lies on \(AB\) with \(CD\perp AB\). Let \(AD=x\), \(DB=y\). Find

1. \(AB\),
2. \(x^2-y^2\),
3. \(x-y\), to 3 significant figures where needed.