99.9*99.9如何简便运算

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99.9*99.9如何简便运算

99.9*99.9如何简便运算
99.9*99.9如何简便运算

99.9*99.9如何简便运算
=(100-0.1)*99.9
=100*99.9-0.1*99.9
=9990-9.99
=9980.01

(100-0.1)×(100-0.1)展开=10000-10-10+0.01=9980.01 望采纳

(100-0.1)^2=10000-0.2*100+0.01=9980.01

99.9*99.9
=99.9^2
=(100-0.1)^2
=100^2-2*100*0.1+0.1^2
=9980.01

=(100-0.1)*99.9
=100*99.9-0.1*99.9
=9990-9.99
=9980.01