Ta có:
1.3.5...19 = 1.2.3.4.5.6...19.20/2.4.6...20
= 1.2.3.4.5.6...19.20/2^10.(1.2.3...10)
= 11.12.13....20/2^10
= 11/2 . 12/2 . 13/2 ... 20/2 ( đpcm)
chứng minh rằng:1.3.5.....19=11/2.12/2.13/2.....20/2
chứng minh rằng :
1.3.5.....19=11/2.12/2....20/2
chứng minh rằng:1.3.5.7.9=11/2.12/2.13/2....20/2
Cmr
1.3.5. ... .19=11/2.12/2. ... .20/2
CMR:
1.3.5.7.....19=11/2.12/2.13/2.....20.2
Chứng minh rằng \(1.3.5....19\) = \(\frac{11}{2}.\frac{12}{2}.\frac{13}{2}.....\frac{20}{2}\)
CMR: 1.3.5....19 = 11/2 . 12/2 . 13/2 ... 20/2
\(CMR:1.3.5...19=\)\(\frac{11}{2}.\frac{12}{2}.\frac{13}{2}...\frac{20}{2}\)
CMR:
1.3.5...19 = \(\frac{11}{2}.\frac{12}{2}.\frac{13}{2}...\frac{20}{2}\)
