用简便算法计算:199.199X198-198.198X199 18.9x178.178+0.49-17.8X189.189
问题描述：
用简便算法计算:199.199X198-198.198X199 18.9x178.178+0.49-17.8X189.189
答
1
=(199*198+0.199*198)-(198*199+0.198*199)
=0.199*198-0.198*199
=0
2
=189x17.8189-17.8x189.189+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
答
199.199*198-198.198*199
=199*1.001*198-198*1.001*199
=0
18.9*178.178+0.49-17.8*189.189
=18.9*178*0.001+0.49-17.8*189*1.001
=18.9*17.8*10*1.001+0.49-17.8*18.9*10*1.001
=0.49