(-5)乘(-25)乘(-2)乘125乘8乘4
=(-5)×(-25)×(-2)×125×8×4
=(-5)×2×(-25)×4×(-125)×8
=(-10)×(-100)×(-1000)
=-1000000
五分之二除以负2又五分之二减二十一分之八×负一又四分之三
=2/5÷(-12/5)-8/21×(-7/4)
=2/5×(-5/12)+8/21×7/4
=-1/6+2/3
=-1/6+4/6
=3/6
=1/2