y'=-4x^3+6x^2-2x满足在(m,2m)小于等于0即可
解方程y’=0,即-2x(2x^2-3x+1)=-2x(2x-1)(x-1)可知在[0,1/2]&[1,+无穷]满足条件m取值为[0,1/4]U[1,+无穷]