函数f(x)=a-x\x-a-1是怎样化简成f(x)=-1-1\x-a-1的,

函数f(x)=a-x\x-a-1是怎样化简成f(x)=-1-1\x-a-1的,
函数f(x)=a-x\x-a-1是怎样化简成f(x)=-1-1\x-a-1的,

函数f(x)=a-x\x-a-1是怎样化简成f(x)=-1-1\x-a-1的,
f(x) = a-x\x-a-1
= a-x+1-1\x-a-1
= a-x+1\x-a-1 - 1\x-a-1
= -(x-a-1)\x-a-1 - 1\x-a-1
= -1-1\x-a-1
这道题的方法是配凑法,观察后面函数f(x)=-1-1\x-a-1中前面的常数项-1,易知分子中应有与分母相同的项.再观察a-x加1后即为x-a-1的相反数,故加减此常数项,使之能拆项后与分母约分,得到-1.再化简便不难得出结果.

f(x)=(a-x)/(x-a-1)=[-(x-a-1)-1]/(x-a-1)
=-1-1/(x-a-1)

看不懂，能加上括号吗