Hello, landlord! Only one formula can be used for this problem, and the solution is as follows: (For convenience, I changed the log in the original problem to lg, which is more scientific) First, left =(lga-lgb)(lgc-lgd), Right = (LGA-LGC) (LGB-LGD)+(LGA-LGD) (LGC-LGB) = LGA LGB-LGA LGD-LGB LGC+LGA LGB-LGB LGD = LGA LGC-LGA LGC-LGA LGD-LGA LGA LGD-. Complete the certificate. Hope to adopt ~