x>=-2 x+2>=0 |x+2|=x+2 x<=3 x-4<=-1 |x-4|=4-x 原式=x+2-3(4-x)=4x-10
x+2-3(4-x)=4x-10
x+2-3(4-x)=x+2-12+3x=4x-10
