Question

Answer 1

`87^2 + 73^2 - 27^2 - 13^2`

`= (87^2 - 13^2) + (73^2 - 27^2)`

`= (87 - 13)(87 + 13) + (73 - 27)(73 + 27)`

`= 74 . 100 + 46 . 100`

`= 100 . (74 + 46)`

`= 100 . 120`

`= 12000`

Answer 2

\(87^2+73^2-27^2-13^2\)

\(=\left(87^2-13^2\right)+\left(73^2-27^2\right)\)

\(=\left(87-13\right)\left(87+13\right)+\left(73-27\right)\left(73+27\right)\)

\(=100\left(87-13+73-27\right)\)

\(=100\cdot\left(60+60\right)=100\cdot120=12000\)