Задача 58507 ...

5f3ea7e3faf909182968ddd9

11.03.2021 22:01:09

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1)
65*75=(70-5)*(70+5)=70^2-5^2=4900-25=4875

2)
73*67=(70+3)*(70-3)=70^2-3^2=4900-9=4891

3)
4,4*5,6=(5-0,6)*(5+0,6)=5^2-0,6^2=25-0,6=24,94

4)
[m]8\frac{1}{4}\cdot 7\frac{3}{4}=(8+\frac{1}{4})\cdot (8-\frac{1}{4})=8^2-(\frac{1}{4})^2=64-\frac{1}{16}=63\frac{15}{16}[/m]