99.9*99.9+19.99巧算

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99.9*99.9+19.99巧算
99.9*99.9+19.99巧算

99.9*99.9+19.99巧算
99.9*99.9+19.99
=(100-0.1)*(100-0.1)+20-0.01
这样你会算下去了把

99.9*99.9+19.99
=(100-0.1)*(100-0.1)+19.99
=100^2-2*0.1*100+0.1^2+19.99
=10000-20+0.01+19.99
=10000