f(x)=(x^2-3x+1)/(x+1) = (x^2+x-4x-4+5)/(x+1) = x - 4 + 5/(x+1)f'(x) = 1 - 5/(x+1)^2 = { (x+1)^2 - 5 ] / (x+1)^2x＞1x∈（1,-1+√5）时,f'(x)＜0,f(x)单调减x∈（-1+√5,+∞）时,f'(x)＞0,f(x)单调增x=-1+√5...那个f’(x)是哪来的？。。。。求解求导啊