①若a＞0，b＞0，则ln⁺（a^b）=bln⁺a

②若a＞0，b＞0，则ln⁺（ab）=ln⁺a+ln⁺b

③若a＞0，b＞0，则 $l{n}^{+}\left(\frac{a}{b}\right)\ge l{n}^{+}a-l{n}^{+}$ b

④若a＞0，b＞0，则ln⁺（a+b）≤ln⁺a+ln⁺b+ln2

其中的真命题有：____．（写出所有真命题的编号）

    There is a National Health Service in Britain. People usually call it "the NHS". When people are ill, they can get free treatment（治疗）. ① The government pays for the treatment. In Britain everyone has a local doctor. The local doctor is a general practitioner (全科医生)(GP). A GP is a doctor who treats patients with all kinds of illness. He may not have specialists (专家) usually work in hospitals.

    If a man is ill and wants to see his doctor, he calls to make an appointment first. If he is too ill and he can't go out, his doctor will come to his house. If the patient has to take medicine, the doctor gives him a prescription(处方). ② The patient has to pay some money for the prescription. He goes to the chemist's shop and buys the medicine there. The price is the same as any kind of medicine. ③But children, students, old people or people without work don't have to pay for their medicine