Question

Tính nhanh:

a) \(38.42\)                               b) \({102^2}\)                          c) \({198^2}\)              d) \({75^2} - {25^2}\)

Answer 1

`a, 38 . 42 = (40-2)(40+2) = 1600 - 4 = 1596`.`

`b, 102^2 = (100+2)^2 = 10000 + 400 + 4 = 10404`

`c, 198^2 = (200-2)^2 = 40000 - 800 + 4 = 39204`

`d, 75^2 - 25^2 = (75+25)(75-25) = 100. 50 = 5000`