=-1×(-1/8)+2÷4+2÷(-1/2)=1/8+1/2-4=-3又3/8
==-1×(-1/8)--（-2）÷4+2÷(-1/2)=-1×(-1/8)+1/2+2÷(-1/2)=1/8+1/2-4=-3又3/8
3又3/8
