原式=AB+3A+BC+C+B+CA+C/A
=(AB+3A+BC+C+B+CA+C/A)XAXBC
=(AB/BC+3AB/BC+B/BC+AC^2B/BC+C^2B/BC+1)XBC
=4AB+2B+C/A+BC
=(4AB+2B+BC^2+BC) /A/BC
=5