下面几道绝对值的数学题大家帮帮忙吧,能做几道就做几道,

一、x>=1,y=2x+6+x-1-4x-4=1-x,y=x>=-1,y=2x+6-x+1-4x-4=3-3x,y==b,y3=x-a+x-b+c-x+d-x=c+d-a-b
b>x>=a,y4=x-a+b-x+c-x+d-x=b+c+d-a-2x4
a>x,y5=a-x+b-x+c-x+d-x=a+b+c+d-4x5,第一感觉y3最小,验证
y3-y1=c+d-a-b-4x1+a+b+c+d=2c+2d-4x1