ta có \(A=\left(\frac{1}{2}-1\right)\left(\frac{1}{3}-1\right).......\left(\frac{1}{10}-1\right)\)
\(A=-\left(\frac{1}{2}.\frac{2}{3}.....\frac{9}{10}\right)\)
\(A=-\frac{1}{10}\)
vi\(-\frac{1}{10}>-\frac{1}{9}\)
do đó A>\(\frac{-1}{9}\)
A=(1/4-1).(1/9-1).(1/16-1)......(1/400-1) . so sanh A voi -1/2
A=\(\left(\frac{1}{2}-1\right).\left(\frac{1}{3}-1\right)...\left(\frac{1}{10}-1\right)\)
So sanh A voi \(-\frac{1}{9}\)
(1/4-1).(1/9-1).....91/400-1) so sanh voi -1/2
A=1/1*2+1/2*3+1/3*4+......+1/99*100 so sanh voi 1
Cho a=(1-1/2)*(1-1/3)*(1-1/4)*...*(1-1/19)*(1-1/20). So sanh a voi 1/21
A=(1/22-1)(1/32-1)(1/42-1)...(1/1002-1)
so sanh A voi 1/2
\(P=\left(\frac{1}{2^2}-1\right).\left(\frac{1}{3^2}-1\right).\left(\frac{1}{4^2}-1\right)...\left(\frac{1}{9^2}-1\right)\)
so sanh P voi 1/2
Cho M=(1\4-1)×(1\9-1)×(1\16-1)×...×(1\81-1)×(1\100-1)
So sanh M voi -11\21
A=1/4+1/42+1/43+.....+1/499
a) Rut gon A
b) So sanh A voi 1/3
