Tính nhanh: a) `89^{3} + 33 . 89^{2} + 3 . 121 . 89 + 11^{3}.` b) `23^{3} - 9 . 23^{2} + 27 . 23 - 27.`

Lời giải:

a)

`89^3+33.89^2+3.121.89+11^3`

`=89^3+3.89^2 .11+3.89.11^2+11^3`

`=(89+11)^3`

`=100^3`

`=1000000`

b)

`23^3-9.23^2+27.23-27`

`=23^3-3.23^2 .3+3.23.3^2-3^3`

`=(23-3)^3`

`=20^3`

`=8000`