Question

Tính  B = 2 2 3 ⋅ 3 2 8 ⋅ 4 2 15 ⋅ 5 2 24 ⋅ 6 2 35 ⋅ 7 2 48 ⋅ 8 2 63 ⋅ 9 2 80 ta được 

A. 9 5

B. 3 5

C.3

D. 6 5

Answer 1

Đáp án cần chọn là: A

B = 2 2 3 ⋅ 3 2 8 ⋅ 4 2 15 ⋅ 5 2 24 ⋅ 6 2 35 ⋅ 7 2 48 ⋅ 8 2 63 ⋅ 9 2 80 = 2.2 1.3 ⋅ 3.3 2.4 ⋅ 4.4 3.5 ⋅ 5.5 4.6 ⋅ 6.6 5.7 ⋅ 7.7 6.8 ⋅ 8.8 7.9 ⋅ 9.9 8.10 = 2.3.4.5.6.7.8.9 1.2.3.4.5.6.7.8. ⋅ 2.3.4.5.6.7.8.9 3.4.5.6.7.8.9.10 = 9 1 ⋅ 2 10 = 9.2 1.10 = 9 5