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\(\left(x-\frac{3}{5}\right)=\frac{2}{5}×-\frac{1}{3}\)
\(\left(x-\frac{3}{5}\right)=-\frac{2}{165}\)
\(x=-\frac{2}{165}+\frac{3}{5}\)
\(x=\frac{97}{165}\)
vậy \(x=\frac{97}{165}\)
\(x×\left(\frac{3}{7}+\frac{2}{3}\right)=\frac{10}{21}\)
\(x×\frac{23}{21}=\frac{10}{21}\)
\(x=\frac{10}{21}:\frac{23}{21}\)
\(x=\frac{10}{23}\)
vậy \(x=\frac{10}{23}\)
\(\left(x-\frac{3}{5}\right):\frac{-1}{3}=\frac{2}{5}\)
=> \(x-\frac{3}{5}=\frac{2}{5}\cdot\left(-\frac{1}{3}\right)=-\frac{2}{15}\)
=> \(x=-\frac{2}{15}+\frac{3}{5}=-\frac{2}{15}+\frac{9}{15}=\frac{7}{15}\)
\(\frac{3}{7}x-\frac{2}{3}x=\frac{10}{21}\)
=> \(\left(\frac{3}{7}-\frac{2}{3}\right)x=\frac{10}{21}\)
=> \(-\frac{5}{21}x=\frac{10}{21}\)
=> \(x=\frac{10}{21}:\frac{-5}{21}=\frac{10}{21}\cdot\frac{-21}{5}=-2\)
Hai bài của ☆luffy cute☆ đều sai hết , xem xét lại đi nhé
Bài 1:
Ta có:
\(y-x=25\Rightarrow y=25+x\)
Mà \(7x=4y\Rightarrow7x=4\cdot\left(25+x\right)\)
\(7x=100+4x\)
\(\Rightarrow7x-4x=100\)
\(3x=100\)
\(x=\frac{100}{3}\)
bài 1 :
Ta có: 7x=4y ⇔ x/4=y/7
áp dụng tính chất dãy tỉ số bằng nhau ta có
x/4=y/7=(y-x)/(7-4)=100/3
⇒x= 4 x 100/3=400/3 ; y = 7 x 100/3=700/3
bài 2
ta có x/5 = y/6 ⇔ x/20=y/24
y/8 = z/7 ⇔ y/24=z/21
⇒x/20=y/24=z/21
ADTCDTSBN(bài 1 có)
x/20=y/24=z/21=(x+y)/(20+24)=69/48=23/16
⇒x= 20 x 23/16 = 115/4
y= 24x 23/16=138/2
z=21x23/16=483/16
a) \(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{z}{7};x+y+z=56\)
\(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{z}{7}=\dfrac{x+y+z}{2+5+7}=\dfrac{56}{14}=4\)
\(\Rightarrow\left\{{}\begin{matrix}x=4.2=8\\y=4.5=20\\z=4.7=28\end{matrix}\right.\)
b) \(\dfrac{x}{1,1}=\dfrac{y}{1,3}=\dfrac{z}{1,4}\left(1\right);2x-y=5,5\)
\(\left(1\right)\Rightarrow\dfrac{2x-y}{1,1.2-1,3}=\dfrac{5,5}{0,9}\)
\(\Rightarrow\left\{{}\begin{matrix}x=1,1.\dfrac{5,5}{0,9}=\dfrac{6,05}{0,9}\\y=1,3.\dfrac{5,5}{0,9}=\dfrac{7,15}{0,9}\\z=\dfrac{1,4}{1,1}.x=\dfrac{1,4}{1,1}.\dfrac{6,05}{0,9}=\dfrac{8,47}{0,99}\end{matrix}\right.\)
d) \(\dfrac{x}{2}=\dfrac{x}{3}=\dfrac{z}{5};xyz=-30\)
\(\dfrac{x}{2}=\dfrac{x}{3}=\dfrac{z}{5}=\dfrac{xyz}{2.3.5}=\dfrac{-30}{30}=-1\)
\(\Rightarrow\left\{{}\begin{matrix}x=2.\left(-1\right)=-2\\y=3.\left(-1\right)=-3\\z=5.\left(-1\right)=-5\end{matrix}\right.\)
\(a,\Leftrightarrow-\dfrac{1}{2}x=\dfrac{1}{4}\Leftrightarrow x=-\dfrac{1}{2}\\ b,\Leftrightarrow\dfrac{1}{6}:x=\dfrac{1}{2}+\dfrac{1}{3}=\dfrac{5}{6}\Leftrightarrow x=\dfrac{1}{6}:\dfrac{5}{6}=\dfrac{1}{5}\\ c,\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{5}=3\\x+\dfrac{1}{5}=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{14}{5}\\x=-\dfrac{16}{5}\end{matrix}\right.\)
\(d,\Leftrightarrow\left(x+\dfrac{1}{2}\right)^2=\dfrac{22}{9}-\dfrac{7}{3}=\dfrac{1}{9}\\ \Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=\dfrac{1}{3}\\x+\dfrac{1}{2}=-\dfrac{1}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{6}\\x=-\dfrac{5}{6}\end{matrix}\right.\\ e,\Leftrightarrow2\left|x\right|=2-\dfrac{1}{2}=\dfrac{3}{2}\\ \Leftrightarrow\left[{}\begin{matrix}2x=\dfrac{3}{2}\\2x=-\dfrac{3}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{4}\\x=-\dfrac{3}{4}\end{matrix}\right.\)
\(f,\Leftrightarrow\left|x+\dfrac{1}{2}\right|=1+\dfrac{1}{6}=\dfrac{7}{6}\\ \Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=\dfrac{7}{6}\\x+\dfrac{1}{2}=-\dfrac{7}{6}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=-\dfrac{5}{3}\end{matrix}\right.\)
e: ta có: \(2\left|x\right|+\dfrac{1}{2}=2\)
\(\Leftrightarrow2\left|x\right|=\dfrac{3}{2}\)
\(\Leftrightarrow\left|x\right|=\dfrac{3}{4}\)
hay \(x\in\left\{\dfrac{3}{4};-\dfrac{3}{4}\right\}\)
nhận giá trị âm tức là giá trị của biểu thức nhỏ hơn 0 và ngược lại!
a) \(15-3x< 0\)
\(\Leftrightarrow-3x< -15\)
\(\Leftrightarrow3x>5\)
b) \(27x+9< 0\)
\(\Leftrightarrow27x< -9\)
\(\Leftrightarrow x< -\frac{1}{3}\)
c) \(2y^2-4x< 0\)
\(\Leftrightarrow2\cdot\left(y^2-2x\right)< 0\)
\(\Leftrightarrow y^2-2x< 0\)
......
a) \(\left(x-3^2\right)^3=\left(3^3\right)^2\)
\(\left(x-3^2\right)^3=3^6\)
\(x-9=9\)
\(x=18\)
b) \(\frac{3x}{2}=\frac{4y}{5}\) và \(y-x=21\)
\(5\cdot3x=2\cdot4y\)
\(15x=8y\)
\(\frac{y}{15}=\frac{x}{8}\)
Áp dụng tính chất của dãy tỉ số bằng nhau:
\(\frac{y}{15}=\frac{x}{8}=\frac{y-x}{15-8}=\frac{21}{7}=3\)
\(\Rightarrow y=3\cdot15=45\)
\(\Rightarrow x=3\cdot8=24\)
c) \(x-\frac{1}{x}+2=x-\frac{2}{x}+3\)
\(x-\frac{1}{x}-x+\frac{2}{x}=3-2\)
\(\frac{1}{x}+\frac{2}{x}=1\)
\(\frac{3}{x}=1\)
\(x=3\)
không làm đâu mệt rùi