1,f(x) = |1 - x| + |x - 2|x < 1,f(x) = 1 - x + 2 - x = 3 - 2x,f(x) 单调递减,f(x)>f(1)=1.1 f(1)=1.只有当 1 f(b)=c-a.c < x,f(x) = x - a + x - b + x - c = 3x - a - b - c,f(x) 单调递增,f(c) = 2c - a - b <...