Tính nhanh `73^2-13^2-10^2+20.13`

`73^2-13^2-10^2+20.13`

`=` `73^2-(13^2-20.13+10^2)`

`=` `73^2-(13-10)^2`

`=` `73^2-3^2`

`=` `(73+3)(73-3)`

`=` `76.70`

`=` `5320`

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