tìm x biết: \(\frac{\left|-x-5\right|}{x+5}=1\)
Tìm x, biết:
a)\(3\left|x+4\right|-\left|2x+1\right|-5\left|x+3\right|+\left|x-9\right|=5\)
b)\(\left|\frac{11}{5}-x\right|+\left|x+\frac{1}{5}\right|+\frac{41}{5}=1,2\)
c)\(2\left|x+\frac{7}{2}\right|+\left|x\right|-\frac{7}{2}=\left|\frac{11}{5}-x\right|\)
Tìm x, biết:
a)\(\left(x+5\right).\left(x+9\right)>0\)
b)\(\left(\frac{1}{7}x-\frac{2}{7}\right).\left(-\frac{1}{5}x+\frac{3}{5}\right).\left(\frac{1}{3}x+\frac{4}{3}\right)=0\)
bạn ơi trả lời được câu này kông
( x + 1 ) + ( x - 3 ) + ( x + 5 ) + ............ + ( x +9) = 35
Bài 1 : Tìm x biết :
a, \(\left|\frac{3}{2}x+\frac{1}{2}\right|=\left|4x-1\right|\)
b, \(\left|\frac{5}{4}x-\frac{7}{2}\right|-\left|\frac{5}{8}x+\frac{3}{5}\right|=0\)
c,\(\left|\frac{7}{5}x+\frac{2}{3}\right|=\left|\frac{4}{3}x-\frac{1}{4}\right|\)
Bài 2 : Tìm x biết :
a, | 2x - 5 | = x +1
b, | 3x - 2 | -1 = x
c, | 3x - 7 | = 2x + 1
d, | 2x-1 | +1 = x
1a) \(\left|\frac{3}{2}x+\frac{1}{2}\right|=\left|4x-1\right|\)
=> \(\orbr{\begin{cases}\frac{3}{2}x+\frac{1}{2}=4x-1\\\frac{3}{2}x+\frac{1}{2}=1-4x\end{cases}}\)
=> \(\orbr{\begin{cases}-\frac{5}{2}x=-\frac{3}{2}\\\frac{11}{2}x=\frac{1}{2}\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{5}{3}\\x=\frac{1}{11}\end{cases}}\)
b) \(\left|\frac{5}{4}x-\frac{7}{2}\right|-\left|\frac{5}{8}x+\frac{3}{5}\right|=0\)
=>\(\left|\frac{5}{4}x-\frac{7}{2}\right|=\left|\frac{5}{8}x+\frac{3}{5}\right|\)
=> \(\orbr{\begin{cases}\frac{5}{4}x-\frac{7}{2}=\frac{5}{8}x+\frac{3}{5}\\\frac{5}{4}x-\frac{7}{2}=-\frac{5}{8}x-\frac{3}{5}\end{cases}}\)
=> \(\orbr{\begin{cases}\frac{5}{8}x=\frac{41}{10}\\\frac{15}{8}x=\frac{29}{10}\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{164}{25}\\x=\frac{116}{75}\end{cases}}\)
c) TT
a, \(\left|\frac{3}{2}x+\frac{1}{2}\right|=\left|4x-1\right|\)
=> \(\orbr{\begin{cases}\frac{3}{2}x+\frac{1}{2}=4x-1\\-\frac{3}{2}x-\frac{1}{2}=4x-1\end{cases}}\)
=> \(\orbr{\begin{cases}\frac{3}{2}x+\frac{1}{2}-4x=-1\\-\frac{3}{2}x-\frac{1}{2}-4x=-1\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{3}{5}\\x=\frac{1}{11}\end{cases}}\)
\(b,\left|\frac{5}{4}x-\frac{7}{2}\right|-\left|\frac{5}{8}x+\frac{3}{5}\right|=0\)
=> \(\left|\frac{5}{4}x-\frac{7}{2}\right|-0=\left|\frac{5}{8}x+\frac{3}{5}\right|\)
=> \(\frac{\left|5x-14\right|}{4}=\frac{\left|25x+24\right|}{40}\)
=> \(\frac{10(\left|5x-14\right|)}{40}=\frac{\left|25x+24\right|}{40}\)
=> \(\left|50x-140\right|=\left|25x+24\right|\)
=> \(\orbr{\begin{cases}50x-140=25x+24\\-50x+140=25x+24\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{164}{25}\\x=\frac{116}{75}\end{cases}}\)
c, \(\left|\frac{7}{5}x+\frac{2}{3}\right|=\left|\frac{4}{3}x-\frac{1}{4}\right|\)
=> \(\orbr{\begin{cases}\frac{7}{5}x+\frac{2}{3}=\frac{4}{3}x-\frac{1}{4}\\-\frac{7}{5}x-\frac{2}{3}=\frac{4}{3}x-\frac{1}{4}\end{cases}}\)
=> \(\orbr{\begin{cases}x=-\frac{55}{4}\\x=-\frac{25}{164}\end{cases}}\)
Bài 2 : a. |2x - 5| = x + 1
TH1 : 2x - 5 = x + 1
=> 2x - 5 - x = 1
=> 2x - x - 5 = 1
=> 2x - x = 6
=> x = 6
TH2 : -2x + 5 = x + 1
=> -2x + 5 - x = 1
=> -2x - x + 5 = 1
=> -3x = -4
=> x = 4/3
Ba bài còn lại tương tự
Tìm x biết :
a, \(\frac{1}{3}.x+\frac{2}{5}.\left(x-1\right)=0\)
b,\(3.\left(x-\frac{1}{2}\right)-5.\left(x+\frac{3}{5}\right)=x+\frac{1}{5}\)
\(\frac{1}{3}x+\frac{2}{5}\left(x-1\right)=0\)
\(\Leftrightarrow\frac{1}{3}x+\frac{2}{5}x-\frac{2}{5}=0\)
\(\Leftrightarrow\frac{11}{15}x=\frac{2}{5}\)
\(\Leftrightarrow x=\frac{2}{5}\div\frac{11}{15}=\frac{2.15}{5.11}=\frac{6}{11}\)
Vậy x = 6/11
a) \(\frac{1}{3}.x+\frac{2}{5}.\left(x-1\right)=0\)
\(\frac{1}{3}.x+\frac{2}{5}.x-\frac{2}{5}=0\)
\(x.\left(\frac{1}{3}+\frac{2}{5}\right)-\frac{2}{5}=0\)
\(x.\frac{11}{15}-\frac{2}{5}=0\)
\(x.\frac{11}{15}=\frac{2}{5}\)
\(x=\frac{2}{5}:\frac{11}{15}\)
\(x=\frac{6}{11}\)
b) \(3.\left(x-\frac{1}{2}\right)-5.\left(x+\frac{3}{5}\right)=x+\frac{1}{5}\)
\(3x-\frac{3}{2}-5x-3=x+\frac{1}{5}\)
\(3x-5x-\left(\frac{3}{2}+3\right)=x+\frac{1}{5}\)
\(-2x-\frac{9}{2}=x+\frac{1}{5}\)
\(\Rightarrow-2x-x=\frac{1}{5}+\frac{9}{2}\)
\(-3x=\frac{47}{10}\)
\(x=\frac{47}{10}:\left(-3\right)\)
\(x=\frac{-47}{30}\)
tìm x biết:
\(\left(\frac{1}{4}x-1\right)-\left(\frac{5}{6}x+2\right)-\left(1-\frac{5}{8}x\right)=3\)
giúp mk vs các bạn ui
\(\left(\frac{1}{4}x-1\right)-\left(\frac{5}{6}x+2\right)-\left(1-\frac{5}{8}x\right)=3\)
=> \(\frac{1}{4}x-1-\frac{5}{6}x-2-1+\frac{5}{8}x=3\)
=> \(\left(\frac{1}{4}x-\frac{5}{6}x+\frac{5}{8}x\right)+\left(-1-2-1\right)=3\)
=> \(\frac{1}{24}x-4=3\)
=> \(\frac{1}{24}x=7\)
=> \(x=7:\frac{1}{24}=7\cdot24=168\)
Vậy x = 168
\(\left(\frac{1}{4}x-1\right)-\left(\frac{5}{6}x+2\right)-\left(1-\frac{5}{8}x\right)=3\)
\(\frac{1}{4}x-1-\frac{5}{6}x-2-1+\frac{5}{8}x=3\)
\(x\left(\frac{1}{4}-\frac{5}{6}+\frac{5}{8}\right)-\left(1+2+1\right)=3\)
\(x.\frac{1}{24}-4=3\)
\(x.\frac{1}{24}=7\)
\(x=7:\frac{1}{24}\)
\(x=168\)
Vậy \(x=168\).
tìm x biết
\(3.\left(x-\frac{1}{2}\right)-5.\left(x-\frac{3}{5}\right)=-x+\frac{1}{5}\)
=> \(\left(3x-\frac{3}{2}\right)-\left(5x-3\right)=-x+\frac{1}{5}
\)
=> \(3x-\frac{3}{2}-5x+3=-x+\frac{1}{5}\)
=> \(3x-5x-\frac{3}{2}+3=-x+\frac{1}{5}\)
=> \(-2x-\left(\frac{3}{2}-3\right)=-x+\frac{1}{5}\)
=> \(-2x-\frac{-3}{2}=-x+\frac{1}{5}\)
=> \(-2x+\frac{3}{2}=-x+\frac{1}{5}\)
=> \(-2x+x=\frac{1}{5}-\frac{3}{2}\)(Chuyển vế)
=> \(x.\left(-2+1\right)=\frac{-13}{10}\)
=> \(x.\left(-1\right)=\frac{-13}{10}\)
=> \(x=\frac{-13}{10}:\left(-1\right)\)
=> \(x=\frac{13}{10}\)
Tìm x biết : \(\left(\frac{1}{7}x-\frac{2}{7}\right)\left(\frac{-1}{5}x+\frac{3}{5}\right)\left(\frac{1}{3}x+\frac{4}{3}\right)=0\)
Tích các thừa số là 0 chứng tỏ có ít nhất một tổng có kết quả là 0
Xét 1/7x - 2/7 = 0
=> 1/7 . x = 2/7
x = 2
Xét -1/5x + 3/5 = 0
=> -1/5 . x = -3/5
x = 3
Xét 1/3x + 4/3 = 0
=> 1/3x = -4/3
x = -4
Tìm x biết : \(3.\left(x-\frac{1}{2}\right)-5\left(x+\frac{3}{5}\right)=\frac{1}{5}\)
3x -3/2 -5x - 3 = 1/5
3x - 5x = 1/5 + 3/2 + 3
-2x = 47/10
x = -47/20
1. Tìm x ϵ Q sao cho:
a) (2x-3). (x+1) < 0.
b) \(\left(x-\frac{1}{2}\right).\left(x+3\right)\)> 0.
2. Tính:
S=\(\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{999.1001}\)
3. Tìm x: Biết x không thuộc{-2; -5; -10; -17}
\(\frac{3}{\left(x+2\right).\left(x+5\right)}+\frac{5}{\left(x+5\right).\left(x+10\right)}+\frac{7}{\left(x+10\right).\left(x+17\right)}=\frac{x}{\left(x+2\right).\left(x+17\right)}\)
Bài 1:
a) (2x-3). (x+1) < 0
=>2x-3 và x+1 ngược dấu
Mà 2x-3<x+1 với mọi x
\(\Rightarrow\begin{cases}2x-3< 0\\x+1>0\end{cases}\)
\(\Rightarrow\begin{cases}x< \frac{3}{2}\\x>-1\end{cases}\)\(\Rightarrow-1< x< \frac{3}{2}\)
b)\(\left(x-\frac{1}{2}\right)\left(x+3\right)>0\)
\(\Rightarrow x-\frac{1}{2}\) và x+3 cùng dấu
Xét \(\begin{cases}x-\frac{1}{2}>0\\x+3>0\end{cases}\)\(\Rightarrow\begin{cases}x>\frac{1}{2}\\x>-3\end{cases}\)
Xét \(\begin{cases}x-\frac{1}{2}< 0\\x+3< 0\end{cases}\)\(\Rightarrow\begin{cases}x< \frac{1}{2}\\x< -3\end{cases}\)
=>....
Bài 2:
\(S=\frac{1}{2}\left(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{999.1001}\right)\)
\(=\frac{1}{2}\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{999}-\frac{1}{1001}\right)\)
\(=\frac{1}{2}\left(\frac{1}{3}-\frac{1}{1001}\right)\)
\(=\frac{1}{2}\cdot\frac{998}{3003}\)
\(=\frac{499}{3003}\)
1. Tìm x ϵ Q sao cho:
a) (2x-3). (x+1) < 0.
b) \(\left(x-\frac{1}{2}\right).\left(x+3\right)>0\)
2.Tính:
S=\(\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{999.1001}\)
3.Tìm x: Biết x không thuộc{-2; -5; -10; -17}
\(\frac{3}{\left(x+2\right).\left(x+5\right)}+\frac{5}{\left(x+5\right).\left(x+10\right)}+\frac{7}{\left(x+10\right).\left(x+17\right)}=\frac{x}{\left(x+2\right).\left(x+17\right)}\)
tự làm nhé. bài cô Kiều cho dễ mừ :)