189乘以178.178+0.49-17.8乘以189.189用简便算法怎样算?

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189乘以178.178+0.49-17.8乘以189.189用简便算法怎样算?

189乘以178.178+0.49-17.8乘以189.189用简便算法怎样算?
189乘以178.178+0.49-17.8乘以189.189用简便算法怎样算?

189乘以178.178+0.49-17.8乘以189.189用简便算法怎样算?
189*(178+0.178)+0.49-178*(189+0.189)
=189*178+189*178*0.001-178*189*0.1-178*189*0.001.+0.49
=1.001*(189*178)-1.001*(178*189)+0.49
=0.49

原式=189×0.1×178×1.001-178×0.1×189×1.001+0.49
=189×0.1×178×1.001-189×0.1×178×1.001+0.49
=0.49

189*(178+0.178)+0.49-178*(189+0.189)
=189*178+189*178*0.001-178*189*0.1-178*189*0.001.+0.49
=1.001*(189*178)-1.001*(178*189)+0.49
=0.49

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