数学简便计算(1)急、在线等..做对加200分6.3+0.47×47-4.7十七分之十三×(十三分之九×18-十三分之九)99×5.7要用简便方法做题.(注:×=乘)
2019-06-25
数学简便计算(1)急、在线等..做对加200分
6.3+0.47×47-4.7
十七分之十三×(十三分之九×18-十三分之九)
99×5.7
要用简便方法做题.(注:×=乘)
优质解答
6.3+0.47×47-4.7
=6.3+4.7×4.7-4.7
=6.3+(5+0.3)(5-0.3)-4.7
=6.3+5²-0.3²-4.7
=6.3+25-0.09-4.7
=26.51
十七分之十三×(十三分之九×18-十三分之九)
=13/17×(9/13×18-9/13)
=13/17×9/13×17
=9
99×5.7=(100-1)×5.7=100×5.7-1×5.7=570-5.7=564.3
6.3+0.47×47-4.7
=6.3+4.7×4.7-4.7
=6.3+(5+0.3)(5-0.3)-4.7
=6.3+5²-0.3²-4.7
=6.3+25-0.09-4.7
=26.51
十七分之十三×(十三分之九×18-十三分之九)
=13/17×(9/13×18-9/13)
=13/17×9/13×17
=9
99×5.7=(100-1)×5.7=100×5.7-1×5.7=570-5.7=564.3