tại vì nó bằng nhau

bang nhau

Giai:

A=1.3.5.7...97.99=\(\frac{\left(1.3.5...97.99\right).\left(2.4.6...100\right)}{2.4.6...100}\)

=\(\frac{1.2.3.4...99.100}{\left(1.2\right).\left(2.2\right)...\left(2.50\right)}\)

=\(\frac{\left(1.2.3...50\right).\left(51.52...99.100\right)}{\left(1.2.3...49.50\right).2^{50}}\)

=\(\frac{51.52...99.100}{2.2...2.2}\)

=\(\frac{51}{2}.\frac{52}{2}.\frac{53}{2}...\frac{100}{2}\)

mà B=\(\frac{51}{2}.\frac{52}{2}.\frac{53}{2}...\frac{100}{2}\)

Nên A=B

Vậy A=B

\(1.3.5.7...97.99=\frac{100!}{2.4.6.8...100}\)

\(=\frac{1.2.3.4...100}{1.2.2.2.3.2...50.2}\)

\(=\frac{51.52.53...100}{2}\)

Vậy \(A=B\)

\(A=1.3.5.....97.99\)

\(=\frac{1.2.3.4......98.99.100}{2.4.6.8......96.98.100}\)

\(=\frac{1.2.3.4....98.99.100}{2.1.2.2.2.3........49.2.50.2}\)

\(=\frac{\left(1.2.3.4......50\right)51.52....98.99.100}{2^{50}\left(1.2.3.......50\right)}\)

\(=\frac{51.52.53.....99.100}{2^{50}}\)

\(=\frac{51}{2}\cdot\frac{52}{2}\cdot\frac{53}{2}\cdot.......\cdot\frac{99}{2}\cdot\frac{100}{2}=B\)

Vậy \(A=B\)

A = 1.3 + 3.5 + 5.7 + ...+ 97.99

6.A = 1.3.(5 + 1) + 3.5.(7 - 1) + 5.7.(9 - 3) + ...+ 97.99.(101 - 95)

6.A = 1.3.5 + 1.3 + 3.5.7 - 1.3.5 + 5.7.9 - 3.5.7 + ...+ 97.99.101 - 95.97.99

6.A = 1.3 +  (1.3.5 + 3.5.7 + 5.7.9 + ...+ 97.99.101) - ( 1.3.5 + 3.5.7 + ...+ 95.97.99)

6.A = 1.3 + 97.99.101 = ...=> A = 

A=1 x 99 x 36 cặp = 3564

Ta có

A = 1.3 + 3.5 + 5.7 + ...+ 97.99

6.A = 1.3.(5 + 1) + 3.5.(7 - 1) + 5.7.(9 - 3) + ...+ 97.99.(101 - 95)

6.A = 1.3.5 + 1.3 + 3.5.7 - 1.3.5 + 5.7.9 - 3.5.7 + ...+ 97.99.101 - 95.97.99

6.A = 1.3 +  (1.3.5 + 3.5.7 + 5.7.9 + ...+ 97.99.101) - ( 1.3.5 + 3.5.7 + ...+ 95.97.99)

làm tiếp nha bn 

hok tốt

(1.2+2.3+3.4......97.98+98.99)+(1+2+3+....98)

=323400+4851=328251

tich nha

 Link nè:https://olm.vn/hoi-dap/detail/1446638519.html

Mk không có đủ thời gian để trình bày lại nên bn đọc bài mk làm và tham khảo nha

Chúc bn học tốt

1.3 + 2.4 + 3.5 +....+ 98.100 
= 1(2+1) + 2.(3+1) + 3.(4+1) +...+ 98(99+1)
= 1.2 + 1 + 2.3 + 2 + 3.4 + 3+....+ 98.99 +98
= (1.2 + 2.3 + 3.4+....98.99) + (1+2+3+....+98)
=323400 + 4851=328251

DE SAI ROI EM EI

D= 1 x 99 x 36 cặp = 3564