Đặt Q =\(\frac{2}{3}.\frac{4}{5}.\frac{6}{7}.\frac{8}{9}.....\frac{400}{401}\)
Dễ thấy: P < Q
Mặt khác:
P.Q = \(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.\frac{4}{5}....\frac{399}{400}.\frac{400}{401}=\frac{1.2.3....399.400}{2.3.4...400.401}\)
=\(\frac{1}{401}< \frac{1}{400}=\left(\frac{1}{20}\right)^2\)
Mà \(P^2< P.Q< \left(\frac{1}{20}\right)^2\Leftrightarrow P< \frac{1}{20}\)
Cho A=1/2.3/4.5/6...99/100
Chứng minh rằng 1/5<A<1/10
chung to rang 8^8 + 2^20 chia het cho 17
Chứng tỏ rằng: \(\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+...+\dfrac{1}{99.100}< \dfrac{1}{2}\)
Cho N =\(\dfrac{1.4}{2.3}+\dfrac{2.5}{3.4}+\dfrac{3.6}{4.5}+...+\dfrac{98.101}{99.100}\)Chứng minh 97<N<98
1/3.4+1/4.5+1/5.6+...+1/20/21
cho a+b=c+d
va a^2+b^2=c^2+d^2
chung minh rang
a^2018+b^2018=c^2018+d^2018
A=5.<2^2.3^2>^9.<2^2>^6-02.<2^2.3>^14.3^4/5.2^28.3^18-7.2^29.3^18
Tính : \(\dfrac{5.2^{30}.3^{18}-2^2.3^{20}.2^{27}}{5.2^9.2^{19}.3^{19}-7.2^{29}.3^{18}}\)
a,Tim so nguyen n de bieu thuc A=8n-9/2n+5 nhan gia tri nguyen.
b,Chung minh1/n.1/n+4=1/4.(1/n-1/n+4)
CAC BAN OI GIUP MINH VOI MAI MINH PHAI KIEM TRA RUI MA BAI KHO QUA CAC BAN OI.CAC BAN NHO GIAI NHANH NHANH GIUM MINH NHE. MINH THE MINH SE TICK CHO.MINH KHN KHOANCAU XIN CAC BAN DO.
