1

2x . 3=3y .4

=> x=2y=>\(\frac{x}{2}=y\Rightarrow\frac{x}{4}=\frac{y}{2}\)

\(\frac{x}{4}=\frac{z}{5}\)

\(\Rightarrow\frac{x}{4}=\frac{y}{2}=\frac{z}{5}=\frac{x-2y+3z}{4-4+15}=\frac{1}{15}=\)

x=1/15x4=4/15

y=1/15x2=2/15

z=1/15x6=1/10

\(\Rightarrow x-y-z=\frac{4}{15}-\frac{2}{15}-\frac{1}{10}=\frac{1}{30}\)

\(\left(2x-3\right)^2-2\left(3x+1\right)^2=2x\left(x-2\right)+\left(x-1\right)\left(x+2\right)\)

4\(x^2\)-12x+9-2(9\(x^2\)+6x+1)=2\(x^2\)-4x+\(x^2\)+2x-x-2

4\(x^2\)-12x+9-18\(x^2\)-12x-2=2\(x^2\)-4x+\(x^2\)+2x-x-2

(4\(x^2\)-18\(x^2\)-2\(x^2\)-\(x^2\)) +(-12x-12x+4x-2x+x)+(9-2+2)=0

-17\(x^2\)-21x+9=0

\(\left|2x-3y\right|+\left|2y+3z\right|+\left|x+y+z\right|=0\)

\(\Rightarrow\left\{{}\begin{matrix}2x-3y=0\\2y+3z=0\\x+y+z=0\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}2x=3y\\3z=-2y\\x+y+z=0\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{3y}{2}\\z=\dfrac{-2y}{3}\\x+y+z=0\end{matrix}\right.\)

\(\Rightarrow x=y=z=0\)

Mình làm một câu để bạn tham khảo, sau đó bạn áp dụng làm các bài còn lại nha ^^

Có gì không hiểu bạn ib nha ^^

1. \(2x=3y-2x\left(1\right)\) và \(x+y=14\)

\(\left(1\right)\Leftrightarrow4x=3y\)

\(\Leftrightarrow\dfrac{x}{3}=\dfrac{y}{4}\)

Theo tính chất dãy tỉ số bằng nhau, có:

\(\dfrac{x}{3}=\dfrac{y}{4}=\dfrac{x+y}{3+4}=\dfrac{14}{7}=2\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=2.3=6\\y=2.4=8\end{matrix}\right.\)

Bạn tự kết luận ^^

sao nhieu bt the ban

\(TH_1:x+y+z=0\Rightarrow\left\{{}\begin{matrix}x+y=-z\\y+z=-x\\x+z=-y\end{matrix}\right.\\ \Rightarrow Q=\dfrac{-z}{z}+\dfrac{-x}{x}+\dfrac{-y}{y}=-3\\ TH_2:x+y+z\ne0\\ \Rightarrow\dfrac{3x-2y+z}{x}=\dfrac{3y-2z+x}{y}=\dfrac{3z-2x+y}{z}=\dfrac{2x+2y+2z}{x+y+z}=2\\ \Rightarrow\left\{{}\begin{matrix}3x-2y+z=x\\3y-2z+x=y\\3z-2x+y=z\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}2x-2y=-z\\2y-2z=-x\\2z-2x=-y\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x-y=-\dfrac{z}{2}\\y-z=-\dfrac{x}{2}\\z-x=-\dfrac{y}{2}\end{matrix}\right.\)

\(\Rightarrow Q=-\dfrac{z}{2}:z-\dfrac{x}{2}:x-\dfrac{y}{2}:y=-\dfrac{1}{2}-\dfrac{1}{2}-\dfrac{1}{2}=-\dfrac{3}{2}\)

=>2x-3y=0 và 2y+3z=0 và x+y+x/z=0

=>x/3=y/2 và y/-3=z/2 và x+y+x/z=0

=>x/9=y/6=z/-4 và x+y+x/z=0

x/9=y/6=z/-4=k

=>x=9k; y=6k; z=-4k

x+y+x/z=0

=>9k+6k+9k/-4k=0

=>15k=9/4

=>k=9/60=3/20

=>x=27/20; y=9/10; z=-3/5