a�0�5+b�0�5+c�0�5+200=12a+16b+20c,(a-6)�0�5+(b-8)�0�5+(c-10)�0�5=0,a=6,b=8,c=10,a�0�5+b�0�5=36+64=100=c�0�5,∴△ABC是直角三角形.
