256x254/255+254x1/255 数学题怎么简算,以及7.2X14.5+17X2.8怎么简算?急!

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256x254/255+254x1/255 数学题怎么简算,以及7.2X14.5+17X2.8怎么简算?急!

256x254/255+254x1/255 数学题怎么简算,以及7.2X14.5+17X2.8怎么简算?急!
256x254/255+254x1/255 数学题
怎么简算,以及7.2X14.5+17X2.8怎么简算?
急!

256x254/255+254x1/255 数学题怎么简算,以及7.2X14.5+17X2.8怎么简算?急!
256x254/255+254x1/255
=(255+1)(255-1)/255+(255-1)*1/255
=(255^2-1)/255+(255-1)*1/255
=255-1/255+1-1/255
=256
7.2X14.5+17X2.8
=(10-2.8)*14.5+17*2.8
=145-2.8*14.5+17*2.8
=145+2.8*(17-14.5)
=145+2.8*2.5
=145+7
=152

把255 当做a (a+1)*(a-1)+(a-1)/a

256*254/255+254*1/255
=(255+1)*254/255+(255-1)*1/255
=255*254/255+254/255*1+255*1/255-1/255*1
=254+254/255+1-1/255
=254+1+(254/255-1/255)
=255+253/255
=255又253/255

原式=(255+1)(255-1)/255+254/255=255+253/255
2)原式=7.2*14.5+(14.5+2.5)(10-7.2)
=7.2*14.5+145-14.5*7.2+25-2.5*7.2=170-18=152

思路:256=255+1,254=255-1,则换算得:
(255+1)×(255-1)/255 + (255-1)/255,计算得:
(255-1/255)+(1-1/255)
算得最后结果:256+2/255
第二题:
=7.2×2.9×5 + 17×2.9 - 17×0.1
=(7.2×5+17)×2.9-1.7
=53×2.9-1.7
=53×(3-0.1)-1.7
=159-(5.3+1.7)
=152