f'(x)=[xf'(x)-f(x)]/x^2<； =0

∴F(x) has not increased.

∴f(a)>； =F(b)

Namely: f (a)/a >; =f(b)/b

Get cross multiplication: af (b)

Do math calmly tomorrow. If not, don't panic, you will win. Bless you:

The college entrance examination was successful!