9.9×9.9+19.9 简便计算
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![9.9×9.9+19.9 简便计算](/uploads/image/z/111654-54-4.jpg?t=9.9%C3%979.9%2B19.9+%E7%AE%80%E4%BE%BF%E8%AE%A1%E7%AE%97)
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9.9×9.9+19.9 简便计算
9.9×9.9+19.9 简便计算
9.9×9.9+19.9 简便计算
9.9×9.9+19.9
=9.9×(10-0.1)+19.9
=9.9×10-9.9×0.1+19.9
=99-0.99+19.9
=99+18.91
=117.91
(10-0.1)(10-0.1)+(20-0.1),然后拆括号