2/x + y/4 = 1/8

=> 2/x = 1/8 - y/4

=> 2/x = 1-2y/8

=> x(1 - 2y) = 16

Ta có: \(\frac{x-y}{3}=\frac{2x+y}{8}=\frac{\left(2x+y\right)-\left(x-y\right)}{8-3}=\frac{x+2y}{5}=\frac{x+2y}{x}\)

\(\Rightarrow x=5\)

Thay \(x=5\)vào biểu thức \(\frac{x-y}{3}=\frac{x+2y}{x}\)ta được

\(\frac{5-y}{3}=\frac{5+2y}{5}\)

\(\Rightarrow5\left(5-y\right)=3\left(5+2y\right)\)

\(\Rightarrow25-5y=15+6y\)

\(\Rightarrow5y+6y=25-15\)

\(\Rightarrow11y=10\)\(\Rightarrow y=\frac{10}{11}\)

Vậy \(x=5\)và \(y=\frac{10}{11}\)

a, => 3.(x-1).27.(x-1) = 8.2

=> 81.(x-1)^2 = 16

=> (x-1)^2 = 16/81

=> x-1=-4/9 hoặc x-1=4/9

=> x=5/9 hoặc x=13/9

b, => \(\sqrt{x}.\left(\sqrt{x}-3\right)\) = 0

=> \(\sqrt{x}=0\)hoặc \(\sqrt{x}-3=0\)

=> x=0 hoặc x=9

Tk mk nha

1, đặt k 2, nhân chéo

Áp dụng tính chất dãy tỉ số bằng nhau 

ta có ; \(\frac{x^2}{4}=\frac{y}{2}=\frac{x^2-3y}{4-\left(3.2\right)}=\frac{-8}{-2}=4.\)

\(\Rightarrow\frac{x^2}{4}=4\Rightarrow x^2=16\Rightarrow x=\pm4\)

\(\Rightarrow\frac{y}{2}=4\Rightarrow y=8\)

b) \(\frac{x+1}{8}=\frac{8}{x+1}\)

\(\Rightarrow\left(x+1\right)^2=64=8^2=\left(-8\right)^2\)

=> x + 1 = 8     => x = 7

x+1 = -8 => x = -9

KL:...

Khi nhân với phân số 1/9 . 27^x sẽ giảm xuống 9 lần còn 3x
Vậy ta biết được 27^x:9=3x
Đổi 9 bằng 3² vậy ta có biểu thức tìm x
27^x=3²+3^x
3^{3  =}3²+3^x
3   = x+2
3-2 = x
 1   = x
 

thanks nhưng mì giải đc òi

1=2018x+2019y≥(2018+2019)2x+y⇒x+y≥(2018+2019)2" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal" class="MathJax_CHTML mjx-chtml">1=2018x+2019y≥(2018+2019)2x+y⇒x+y≥(2018+2019)2

xy=20182019" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; overflow-wrap:normal; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal" class="MathJax_CHTML mjx-chtml">xy=√20182019

sorry mấy bạn =x+y+z chứ ko phải =x+y=z :P 

Dùng tính chất tỉ lệ thức:

\(\frac{x}{\left(y+z+1\right)}=\frac{y}{\left(x+z+1\right)}=\frac{z}{\left(x+y-2\right)}=0\Rightarrow x=y=z=0\) 

Áp dụng tính chất tỉ lệ thức: 

\(x+y+z=\frac{x}{\left(y+z+1\right)}=\frac{y}{\left(x+z+1\right)}=\frac{z}{\left(x+y-2\right)}=\left(\frac{x+y+z}{2x+2y+2z}\right)=\frac{1}{2}\)

=> x+y+z = \(\frac{1}{2}\)

+) \(2x=y+z+1=\frac{1}{2}-x+1\Rightarrow x=\frac{1}{2}\)

+) \(2y=x+z+1=\frac{1}{2}-y+1\Rightarrow y=\frac{1}{2}\) 

+) \(z=\frac{1}{2}-\left(x+y\right)=\frac{1}{2}-1=\frac{-1}{2}\)

TA CÓ: \(\frac{x}{z+y+1}=\frac{y}{x+z+1}=\frac{z}{x+y-2}=\frac{x+y+z}{z+y+1+x+z+1+x+y-2}=\frac{1.\left(x+y+z\right)}{\left(1+1-2\right)+2x+2y+2z}\)

\(=\frac{1.\left(x+y+z\right)}{0+2.\left(x+y+z\right)}=\frac{1.\left(x+y+z\right)}{2.\left(x+y+z\right)}=\frac{1}{2}\)

\(\Rightarrow x+y+z=\frac{1}{2}\)

\(\Rightarrow\frac{x}{z+y+1}=\frac{1}{2}\)\(\Rightarrow2x=z+y+1\)\(\Rightarrow3x=x+z+y+1\)\(\Rightarrow3x=\frac{1}{2}+1\Rightarrow3x=\frac{3}{2}\Rightarrow x=\frac{1}{2}\)

\(\frac{y}{x+z+1}=\frac{1}{2}\)\(\Rightarrow2y=x+z+1\Rightarrow3y=y+x+z+1\Rightarrow3y=\frac{1}{2}+1=\frac{3}{2}\Rightarrow y=\frac{1}{2}\)

\(\frac{z}{x+y-2}=\frac{1}{2}\)\(\Rightarrow2z=x+y-2\Rightarrow3z=x+y+z-2\Rightarrow3z=\frac{1}{2}-2=\frac{-3}{2}\Rightarrow z=\frac{-1}{2}\)

VẬY X= 1/2; Y= 1/2 ; Z= -1/2

CHÚC BN HỌC TỐT!!!!!!