因为,2.57,7的循环 = 2.57+7/900 ,
(2.57+7/900)a-2.57a = 0.7 ,
(7/900)a = 0.7 ,
a = 90 ,
所以,2.57,7的循环乘以a = (2.57+7/900)a = 232 .