计算2*3*4*5*(1/2-1/3+1/4-1/5)=3×4×5-2×4×5+2×3×5-2×3×4
=60-40+30-24=90-64=26
使用乘法分配率
原式=3*4*5-2*4*5+2*3*5-2*3*4
=(3-2)*4*5+(5-4)*2*3
=20+6
=26
2*3*4*5*(1/2-1/3+1/4-1/5)
=2*3*4*5*1/2-2*3*4*5*1/3+2*3*4*5*1*4-2*3*4*5*1/5
=3*4*5-2*4*5+2*3*5-2*3*4
=60-40+30-24
=26