如图所示是函数f(x)=x^3+bx^2+cx+d的大致图象,则x1+x2=

f(0) = d = 0 f(-1) = -1 + b - c + d = 0 f(2) = 8 + 4b + 2c + d = 0 b = -1 , c= -2 , d = 0 f(x) = x³ - x² -2x f'(x) = 3x² - 2x -2 3x² - 2x - 2 = 0 x1 + x2 = 2/3