TÍNH:
1+\(\dfrac{1}{3}\)+\(\dfrac{1}{9}\)+\(\dfrac{1}{27}\)+\(\dfrac{1}{81}\)
AI BÍT TÍNH NHANH BÀI NÀY NỮA THÌ CHỈ MÌNH VỚI !!!!!
(Òwó)❤❤❤
(\(x\) : 2,2 )x \(\dfrac{1}{6}\) = \(\dfrac{-3}{8}\)x (0,5 - \(1\dfrac{3}{5}\))
giúp mình câu này đc ko ạ , mình đang cần gấp
❤❤❤❤
\(\left(x:2,2\right)\times\dfrac{1}{6}=\dfrac{-3}{8}\times\left(0,5-1\dfrac{3}{5}\right)\)
\(\Rightarrow\left(x:2,2\right)\times\dfrac{1}{6}=\dfrac{-3}{8}\times\left(\dfrac{1}{2}-\dfrac{8}{5}\right)\)
\(\Rightarrow\left(x:2,2\right)\times\dfrac{1}{6}=\dfrac{-3}{8}\times\dfrac{11}{10}\)
\(\Rightarrow\left(x:2,2\right)\times\dfrac{1}{6}=\dfrac{33}{80}\)
\(\Rightarrow x:2,2=\dfrac{33}{80}:\dfrac{1}{6}\)
\(\Rightarrow x:2,2=\dfrac{99}{40}\)
\(\Rightarrow x=\dfrac{99}{40}\times2,2\)
\(\Rightarrow x=\dfrac{1089}{200}\)
=>(x:2,2)*1/6=-3/8(1/2-8/5)=33/80
=>x:2,2=99/40
=>x=1089/200
a) \(\dfrac{\left(-3\right)^x}{81}\) = -27
b) [x-\(\dfrac{1^2}{2}\)] = 25
giúp dùm tớ với nha ❤❤❤
\(a,\Rightarrow\dfrac{\left(-3\right)^x}{\left(-3\right)^4}=\left(-3\right)^3\\ \Rightarrow\left(-3\right)^{x-4}=\left(-3\right)^3\\ \Rightarrow x-4=3\Rightarrow x=7\\ b,Sửa:\left(x-\dfrac{1}{2}\right)^2=25\Rightarrow\left[{}\begin{matrix}x-\dfrac{1}{2}=5\\x-\dfrac{1}{2}=-5\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{11}{5}\\x=-\dfrac{9}{5}\end{matrix}\right.\)
TÍNH GIÚP MÌNH
A=\(\dfrac{1}{1.2}\)+\(\dfrac{1}{2.3}\)+\(\dfrac{1}{3.4}\)+...+\(\dfrac{1}{99.100}\)
THANK YOU!!!❤
A=\(\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+.....+\dfrac{1}{99}-\dfrac{1}{100}\)
=\(\dfrac{1}{1}-\dfrac{1}{100}\)
=\(\dfrac{99}{100}\)
\(A=\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{99.100}\)
\(A=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{99}-\dfrac{1}{100}\)
\(A=1-\dfrac{1}{100}=\dfrac{99}{100}\)
Cho a≥ 0. Chứng minh rằng:
\(a-\sqrt{a}+1=\left(\sqrt{a}-\dfrac{1}{2}\right)^2+\dfrac{3}{4}\)
Mọi người giúp mk với nha! Thank you!❤❤❤❤❤
Lớp 9 học hđt rồi bạn nhỉ \(VT=a-\sqrt{a}+1=a-\sqrt{a}+\dfrac{1}{4}+\dfrac{3}{4}=\left(\sqrt{a}-\dfrac{1}{2}\right)^2+\dfrac{3}{4}=VP\)
S = \(81\) + \(27\) + \(9\) + \(3\) ... + \(\dfrac{1}{27}\) + \(\dfrac{1}{81}\)
Tính S giúp mik với ạ, ai nhanh mik tick
\(3S=241+81+27+9+...+\dfrac{1}{9}+\dfrac{1}{27}\)
\(2S=3S-S=241-\dfrac{1}{81}=\dfrac{241x81-1}{81}\)
\(\Rightarrow S=\dfrac{241x81-1}{2x81}\)
Câu hỏi today của CLB Yêu Toán❤❤
+ Dễ: \(\left|\dfrac{1}{2}+x\right|-1=\dfrac{11}{2}\); \(1mm=?km\)
+ Khó: \(\left(\dfrac{1}{2}-1\right).\left(\dfrac{1}{3}-1\right).\left(\dfrac{1}{4}-1\right)...\left(\dfrac{1}{2014}-1\right)\)
Bonus: Số nghịch đảo của 50% ?
a)\(\left|\dfrac{1}{2}+x\right|-1=\dfrac{11}{2}\)
\(\Rightarrow\left|\dfrac{1}{2}+x\right|=\dfrac{11}{2}+1=\dfrac{13}{2}\)
\(\Rightarrow\left[{}\begin{matrix}\dfrac{1}{2}+x=\dfrac{-13}{2}\\\dfrac{1}{2}+x=\dfrac{13}{2}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-7\\x=6\end{matrix}\right.\)
b)\(\left(\dfrac{1}{2}-1\right)\left(\dfrac{1}{3}-1\right)\left(\dfrac{1}{4}-1\right)...\left(\dfrac{1}{2014}-1\right)\)
\(=\dfrac{-1}{2}.\dfrac{2}{-3}.\dfrac{-3}{4}...\dfrac{2012}{-2013}.\dfrac{-2013}{2014}\)
\(=\dfrac{-1}{2014}\)
số nghịch đảo của 50% là:\(\dfrac{100}{50}=2\)
Giải:
Dễ:
|1/2+x|-1=11/2
|1/2+x| =11/2+1
|1/2+x| =13/2
⇒1/2+x=13/2 hoặc 1/2+x=-13/2
x=6 hoặc x=-7
1mm=0,000001km
Khó:
(1/2-1).(1/3-1).(1/4-1).....(1/2014-1)
=-1/2.-2/3.-3/4.....-2013/2014
=-1/2014
Bonus: Số nghịch đảo của 50% là 100/50 =2
Tính tổng sau : \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)
giúp mik nha, nhớ lm cả lời giải nx nhe. THANK YOU!!!!❤
Có công thức \(\dfrac{x}{a\left(a+x\right)}=\dfrac{1}{a}-\dfrac{1}{a+x}\) nhé!
Ví dụ: \(\dfrac{2}{2.4}=\dfrac{1}{2}-\dfrac{1}{4}\)
\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)
\(=\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{7}-\dfrac{1}{8}\)
\(=1-\dfrac{1}{8}=\dfrac{7}{8}\)
Dấu . tức là nhân nhé!
\(\left\{{}\begin{matrix}\dfrac{3}{x-1}-\dfrac{1}{y+2}=\dfrac{3}{4}\\\dfrac{5}{x-1}+\dfrac{3}{y+2}=\dfrac{29}{12}\end{matrix}\right.\)giải chi tiết giúp mình nha☘⚽✿❤ mình cảm ơn nha