20a = 20/1.21 + 20/2.22+ ... + 20/80.100
= 1-1/21 + 1/2 - 1/22 +...+ 1/80 - 1/100
= 1 + 1/2 + 1/3 +... + 1/19 + 1/20 - 1/81 - 1/82 -.... - 1/100
80b = 80/1.81 + 80/2.82 + 80/3.83 +... + 80/20.100
= 1 - 1/81+ 1/2 - 1/83 +...+ 1/20 - 1/100
=> 20a = 80b
=> a/b = 4
Câu 24 : Cho A = 1.21 + 1/2.22 + 1/3.23 + ... + 1/80.100 ; B = 1/1.81 + 1/2.82 + 1/3.83 + ... + 1/20.100 . Tính A/B
Cho \(A=\dfrac{1}{1.21}+\dfrac{1}{2.22}+\dfrac{1}{3.23}+...+\dfrac{1}{80.100}\);
\(B=\dfrac{1}{1.81}+\dfrac{1}{2.82}+\dfrac{1}{3.83}+...+\dfrac{1}{20.100}\).
Tính \(\dfrac{A}{B}\).
cho a = 1/1.21 + 1/2.22+...+1/80.100 b= 1/1.81 + 1/2.82+...+1/20.100 tính a/b
Cho A=1/1.21+1/1.22+1/3.23+...+1/80.100
B=1/1.81+1/2.82+1/3.83+...+1/20.100
Tính A/B
Cho \(A=\frac{1}{1.21}+\frac{1}{2.22}+\frac{1}{3.23}+......+\frac{1}{80.100}\)
\(B=\frac{1}{1.81}+\frac{1}{2.82}+\frac{1}{3.83}+....+\frac{1}{20.100}\). Tính \(\frac{A}{B}\)
Tính \(\frac{A}{B}\)
A=\(\frac{1}{1.21}+\frac{1}{2.22}+\frac{1}{3.23}+.....+\frac{1}{80.100}\)
B=\(\frac{1}{1.81}+\frac{1}{2.82}+\frac{1}{3.83}+.....+\frac{1}{20.100}\)
A=\(\frac{1}{1.21}\)+\(\frac{1}{2.22}\)+\(\frac{1}{3.23}\)+...+\(\frac{1}{80.100}\)và B=\(\frac{1}{1.81}\)+\(\frac{1}{2.82}\)+\(\frac{1}{3.83}\)+...+\(\frac{1}{20.100}\).Tính \(\frac{A}{B}\)
A=1/1.21+ 1/2.22 +1/3.23+..........1/80.100 B=1/1.81+1/2.82+1/3.83+............+1/20.100
tính A/B
các bạn giải giúp mình nha. Thanks !
Câu 24 : Cho A = 1/1.21 + 1/2.22 + 1/3.23 + ...+ 1/80.10
