\(1\cdot3\cdot5\cdot...\cdot19=\dfrac{1\cdot2\cdot3\cdot4\cdot...\cdot17\cdot18\cdot19\cdot20}{2\cdot4\cdot6\cdot8\cdot...\cdot20}\)
\(=\dfrac{1\cdot2\cdot3\cdot4\cdot...\cdot17\cdot18\cdot19\cdot20}{1\cdot2\cdot2\cdot2\cdot3\cdot2\cdot4\cdot2\cdot...\cdot10\cdot2}\)
\(=\dfrac{11}{2}\cdot\dfrac{12}{2}\cdot...\cdot\dfrac{18}{2}\cdot\dfrac{19}{2}\)
CMR
1.3.5. ... .19 = 11/2.12/2. ... .20/2
CMR
1.3.5. ... .19 = 11/2.12/2. ... .20/2
CMR
1.3.5. ... .19 = 11/2.12/2. ... .20/2
CMR
1.3.5. ... .19 = 11/2.12/2. ... .20/2
CMR 1.3.5...19=\(\dfrac{11}{2}.\dfrac{12}{2}.\dfrac{13}{2}...\dfrac{20}{2}\)
CMR
1-1/2+1/3-1/4+1/5-1/6+...+1/19-1/20=1/11+1/12+...+1/21
CMR
1-1/2+1/3-1/4+1/5-1/6+...+1/19-1/20=1/11+1/12+...+1/21
CMR \(1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{5}-\dfrac{1}{6}+...+\dfrac{1}{19}-\dfrac{1}{20}=\dfrac{1}{11}+\dfrac{1}{12}+\dfrac{1}{13}+...+\dfrac{1}{20}\)
Rút gọn biểu thức :
\(\frac{5^2.6^{11}.16^2+6^2.12^6.15^2}{2.6^{12}.10^4-81^2.960^3}\)
\(\frac{\left(5^2.6^{11}.16^2+6^2.12^6.15^2\right).10}{2.6^{12}.10^4-81^2.960^3}\)
Giải ra bn nhé !
