已知f（x）=lg（ax-bx）（a，b为常数）， ①当a，b＞0且a≠b时，求

Forgetful President
George Washington was the first president of the United States.   小题1:  But it seems that the president was not a perfect person.
A New York library recently found that Washington borrowed two books from the library in 1789.    小题2:  If he were still alive, he would have to pay the library$300, 000 in fines（罚款）, for it has been late for over 220 years.
On October 5, 1789, George Washington went to the New York Society Library.
  小题3:  He didn’t sign his name in the borrower’s book. He just wrote “President” to show who had taken them out.
The two books should have been brought back a month later, but they were never returned. Workers at the library realized the books were missing when they organized the library’s old records. The New York Society Library doesn’t expect anyone to pay the fine.   小题4: 

A. It’s said that he never told a lie. B. He then borrowed the books from it. C. However, he didn’t return them on time. D. But it hopes that someone will return the books. E. He kept the books, because he didn’t finish reading them.