短語詞組短語repeating g decimal 循環(huán)小數mixed repeating decimal 混循環(huán)小數pure repeating decimal 純循環(huán)小數a repeating decimal 循環(huán)小數repeating decimal fraction 循環(huán)小數period of a repeating decimal 小數循環(huán)節(jié) 返回 repeating decimal