25．在ΔABC\Delta ABCΔABC中，∠A=90∘\angle A=90\circ∠A=90∘，AB=6AB=6AB=6，AC=8AC=8AC=8，点OOO为ΔABC\Delta ABCΔABC外接圆的圆心，则AO→⋅BC→=\overrightarrow{AO}\cdot \overrightarrow{BC}=AO⋅BC=[ 14 ]．