原式=(1-1/2)×2(1-1/3)×3(1-1/4)×4(1-1/5)×5(1-1/6)×6(1-1/7)×7(1-1/8)
=(1×2×3×4×5×6×7)×(1/2×2/3×3/4×4/5×5/6×6/7×7/8)
=(1×2×3×4×5×6×7)×1/8
=630
(1-1/2)×(2-2/3)×(3-3/4)×(4-4/5)×(5-5/6)×(6-6/7)×(7-7/8)
=(1-1/2)×2×(1-1/3)×3×(1-1/4)×4×(1-1/5)×5×(1-1/6)×6×(1-1/7)×7×(1-1/8)
=2×3×4×5×6×7×(1/2)×(2/3)×(3/4)×(4/5)×(5/6)×(6/7)×(7/8)
=2×3×4×5×6×7×(1/8)
=3×4×6×7x1/4
=3x6x7
=126