1.(2-1)x(3-4)x(6-5)=12.(3-2-1)+(5-4)x(7-6)=13.(2-1)x(4-3)x(6-5)x(8-7)=14.(3-2-1)+(5-4)x(7-6)x(9-8)=1
(1-2)×(3-4)×(5-6)×(7-8)=1
