Question

Tính nhanh:

a) 49²                                        b) 51²

c) 99.100

Answer 1

a) = (50-1)^2 = 50^2 - 2.50 + 1 = 2500 - 100 + 1 = 2401

Answer 2

b) = (50+1)^2 = 50^2 + 2.50 + 1 = 2601

Answer 3

c) = 9900

Answer 4

a) 49²                    b) 51²                       c) 99.100

= 49 . 49                 = 51 . 51                   = 9900

= 2401                    = 2601

Answer 5

a. (50 - 1)²

= 50² - 100 + 1

= 2500 - 100 + 1

= 2401

b. (50 + 1)²

= 50² + 100 + 1

= 2500 + 100 + 1

= 2601

c. 99 . 100

= 9900 

Answer 6

a: \(49^2=\left(50-1\right)^2=2401\)

b: \(51^2=\left(50+1\right)^2=2601\)

c: \(99\cdot100=9900\)