(2.1.2 + 1/1.2) + (2.2.3 + 1/2.3) + (2.3.4 + 1/3.4) + (2.4.5 + 1/4.5)+...+(2.9.10 + 9/10) = ?
anh chị giúp em nhé
\(x = {{2.1.2+1} \over 1.2}+{{2.2.3+1} \over 2.3}+ {{2.3.4+1} \over 3.4}+{{2.4.5+1} \over 4.5}+...+{{2.9.10+1} \over 9.10}\)
(2.1.2+1/1.2) + (2.2.3+1/2.3) + (2.3.4+1/3.4) +...+ (2.9.10/9.10) = ?
3. \(\frac{\left(1+2^2+3^2+...+2005^2\right).12}{2.3+4.6+6.9+...+4010.6015}\)
GIẢI CHI TIẾT NHA. LẸ NHA. THANKS
\(1,\frac{3737.43-4343.37}{1^2+2^3+...+27^2}=\frac{101.43.37-101.43.37}{..........}=0\)
1/1.2+1/2.3+1/3.4+1/4.5+...+1/99.100
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{99}-\dfrac{1}{100}=1-\dfrac{1}{100}=\dfrac{99}{100}\)
Cho A=1/1.2 + 1/2.3 + + 1/ 3.4+...+1/49.50 ; B = 1.2+2.3+3.4+4.5+5.6+...+49.50
Tính 50 mủ 2 A – B/17
1/1.2+1/2.3+1/3.4+1/4.5+1/5.6 = ?
=1-1/2+1/2-1/3+......+1/5-1/6
=1-1/6
=5/6
Tick
A=1/1.2+1/2.3+1/3.4+1/4.5+....+1/2018.2019
A= \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{2018.2019}\)
A= 1 - \(\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-...+\frac{1}{2018}-\frac{1}{2019}\)
A= 1 - \(\frac{1}{2019}\)
A= \(\frac{2018}{2019}\)
\(A=\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+...+\frac{1}{2018\cdot2019}\)
\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{2018}-\frac{1}{2019}\)
\(A=1-\frac{1}{2019}\)
\(=\frac{2018}{2019}\)
Vậy \(A=\frac{2018}{2019}\)
HOK TỐT ==.==
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+......+\frac{1}{2018.2019}\)
\(\Rightarrow A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-.....-\frac{1}{2019}\)
\(\Rightarrow A=1-\frac{1}{2019}\)
\(\Rightarrow A=\frac{2019}{2019}-\frac{1}{2019}=\frac{2018}{2019}\)
Vậy A = \(\frac{2018}{2019}\)
S=1/1.2+1/2.3+1/3.4+1/4.5+....+1/99.100
bạn tách ra, 1/1.2=1-1/2 cứ như thế, rồi trừ đi còn 1-1/100=99/100
A = 1/1.2 + 1/2.3 + 1/3.4 + 1/4.5 + 1/5.6
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}\)
\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
\(A=1-\frac{1}{6}\)
\(A=\frac{5}{6}\)
_Chúc bạn học tốt_
Ta có : \(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}\)
\(=1-\frac{1}{5}=\frac{4}{5}\)
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}\)
\(A=\frac{1}{1}-\frac{1}{2}+\frac{1}{3}_{ }-\frac{1}{4}+\frac{1}{5}-\frac{1}{6}\)
\(A=1-\frac{1}{6}\)
\(A=\frac{5}{6}\)