\(\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}+...+\dfrac{1}{n}-\dfrac{1}{n+1}=\dfrac{3}{10}\)
\(\dfrac{1}{3}-\dfrac{1}{n+1}=\dfrac{3}{10}\)
\(\dfrac{-1}{\left(n+1\right)}=\dfrac{-1}{30}\)
\(-n-1=-30\)
-n = -29
n = 29
tìm n thuộc N biết:
\(\dfrac{1}{3.4}\)+\(\dfrac{1}{4.5}\)+\(\dfrac{1}{5.6}\)+....+\(\dfrac{1}{n\left(n+1\right)}\)=\(\dfrac{3}{10}\)
Cho M=1/2.3/4.5/6...99.100 va N=2/3.4/5.6/7.... 100/101 va N=2/3.4/5.6/7..100/101
a) So sanh M va N b) Tinh M.N c) So sanh M va 1/10
cho M= 1/2.3/4.5/6.....99/100 và N= 2/3.4/5.6/7.....100/101
chứng minh m<n
tìm tích m.n
chưng minh m<1/10
tính giá trị biểu thức
A =\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}\)
B = \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{n.\left(n+1\right)}\)(n\(\in\)Z, n\(\ne\)0; n\(\ne\)-1)
c) 1/3.4 + 1/4,5 + 1/5.6 + .... + 1/x.(x + 1) = 3/10 và x thuộc N
tìm x, biết
1/3.4+1/4.5+1/5.6+1/6.7+...+1/x.(x+1)=3/10
Tìm x:
1/3.4+1/4.5+1/5.6+1/6.7+....+1/x(x+1)=3/10
Cho m = 1/2.3/4.5/6....99/100
n= 2/3.4/5.6/7....100/101
CMR: M<N
Cho M = 1/2.3/4.5/6....99/100
N= 2/3.4/5.6/7.....100/101
Tính M,N
