18.9x178.178+0.49-17.8x189.189如何简算?

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18.9x178.178+0.49-17.8x189.189如何简算?

18.9x178.178+0.49-17.8x189.189如何简算?
18.9x178.178+0.49-17.8x189.189如何简算?

18.9x178.178+0.49-17.8x189.189如何简算?
18.9x178.178+0.49-17.8x189.189
=189x178.189-17.8x189.189+0.49
=(189x17.8+189x0.0189)-17.8x189.189+0.49
=17.8x(189-189.189)+17.8x0.0189+0.49
=17.8x0.0189-17.8x0.0189+0.49
=0.49

18.9x178.178+0.49-17.8x189.189
=189*178*0.1*(1.001-1.001)+0.49
=0.49