费费数学第三部分第43题

xiaoyue

题目是TU是两位数, TU is twice product of these digits, U=?

求解方法是: 2TU=10T+U-->U=10T/2T-1-->10T-5+5/(2T-1)-->5+(5/(2T-1))

请教如何推算出等式:5+(5/(2T-1))

谢谢!