23.已知函数f(x)=ea−xf(x)=e^{a-x}f(x)=ea−x.(1)求y=f(x)y=f(x)y=f(x)在x=ax=ax=a处的切线;(2)若0<a<20<a<20<a<2,证明当x>0x>0x>0时,f(x)<ax+2f(x)<\frac{a}{x}+2f(x)<xa+2.