解:8/17×2/25+2/17×9/25 =8/17×2/25+9/17×2/25 =(8/17+9/17)×2/25 =1×2/25 =2/25
=2/17×4×2/25=2/17×9/25=2/17×8/25=2/17×9/25=2/17×(8/25+9/25)=2/17×17/25=2/25