2.84乘(8.5减1.2)怎么简便计算

23.5×5.66-23.4×5.67
=(23.4+0.1)×5.66-23.4×5.67
=23.4×5.66+0.1×5.66-23.4×5.67
=0.1×5.66-23.4×(5.67-5.66)
=0.566-23.4×0.01
=0.566-0.234
=0.332
1.2/(1.2/2.3)/(2.3/3.4)/(3.4/4.5)
=1.2×(2.3/1.2)×(3.4/2.3)×(4.5/3.4)
=4.5