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 + 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

(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

DE SAI ROI EM EI

D= 1 x 99 x 36 cặp = 3564

E = 1.3 + 2.4 + 3.5 +...+ 97.99 + 98.100

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

B = 2.4 + 4.6 + 6.8 + ... + 98.100

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

6A = 1.3.6 + 3.5.6 + 5.7.6 +...+ 97.99.6

1.3.6 = 1.3.(5+ 1) = 1.3.5 + 1.3.1

3.5.6 = 3.5(7 - 1) = 3.5.7 - 1.3.5

5.7.6 = 5.7.(9 - 3) = 5.7.9 - 3.5.7

7.9.6 = 7.9.(11 - 5) = 7.9.11 - 5.7.9

..........................................................................

97.99.6 = 97.99.(101 - 95) = 97.99.101 - 95.97.99

Cộng vế với vế ta có:

6A = 1.3.1 + 97.99.101

6A = 3 + 969903

6A = 969906

A = 969906 : 6

A = 161651

B = 2.4 + 4.6 + 6.8 + ... + 98.100

6B = 2.4.6 + 4.6.6 + 6.8.6 + ... + 98.100.6

2.4.6 = 2.4.6

4.6.6 = 4.6.(8 - 2) = 4.6.8 - 2.4.6

6.8.6 = 6.8.(10 - 4) = 6.8.10 - 4.6.8

8.10.6 = 8.10.(12 - 6) = 8.10.12 - 6.8.10

...............................................................................

98.100.6 = 98.100.(102 - 96) = 98.100.102 - 96.98.100

6B = 98.100.102

B = 98.100.102 : 6

B = 166600

E = A + B

E = 161651 + 166600

E = 328251