y=1/x则，y'=-1/x²所以，y'(1)=-1所以在点(1,1)处的切线为：y-1=(-1)(x-1)=-x+1即：x+y-2=0
y = 1/xy ' = -1/x^2k = -1/1 = -1y-1=-(x-1)x+y-2=0
