Câu 1:

\(y:7+296=431\\ y:7=135\\ y=135\times7\\ y=945\)

Câu 2:

\(2854-y=3175-1614\\ 2854-y=1561\\ y=2854-1561\\ y=1293\)

câu `1`

`y : 7 + 296 = 431`

`=> y :7= 431-296`

`=> y :7=135`

`=>y=135 xx 7`

`=>y=945`

câu `2`

`2854 - y =3175-1614`

`=>2854 - y =1561`

`=> y=2854 -1561`

`=> y=1293`

`@  `\(\text{ Ng Baoo Thuu}\)

`1)` `y:7+296=431`

`y:7=431-296`

`y:7=135`

`y=135xx7`

`y=945`

`2)`

`2854-y=3175-1614`

`2854-y=1561`

`y=2854-1561`

`y=1293`

`#lv`

a) 2y - 12y = 0

\(\Rightarrow\) y ( 2-12) = 0

\(\Rightarrow\) y . (-10) =0 

\(\Rightarrow\) y = 0 : (-10) = 0

b) (y-7)(y-8) = 0

\(\Rightarrow\orbr{\begin{cases}y-7=0\\y-8=0\end{cases}\Rightarrow\orbr{\begin{cases}y=0+7\\y=0+8\end{cases}\Rightarrow}\orbr{\begin{cases}y=7\\y=8\end{cases}}}\)

c) x + x.2+x.3+x.4+...+x.10 = 165

\(\Rightarrow\) x ( 1+2+3+.....+8+9+10) = 165

\(\Rightarrow\)x . \(\frac{\left(1+10\right).10}{2}\)=165

\(\Rightarrow\) x . 55 = 165

\(\Rightarrow x=\frac{165}{55}=3\)

Can you k for me ,Lê Thị Kim Chi!

a) \(2y-12y=0\)

\(\Leftrightarrow-10y=0\)

\(\Leftrightarrow y=0:\left(-10\right)\)

\(\Leftrightarrow y=0\)

b) \(\left(y-7\right)\left(y-8\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}y-7=0\\y-8=0\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}y=0+7\\y=0+8\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}y=7\\y=8\end{cases}}\)

c) \(x+x.2+x.3+......+x.10=165\)

\(\Leftrightarrow x.\left(1+2+3+.....+10\right)=165\)

\(\Leftrightarrow x.55=165\)

\(\Leftrightarrow x=165:55\)

\(\Leftrightarrow x=3\)

\(xy+3x-y=6\\ \Rightarrow x\left(y+3\right)-y-3=3\\ \Rightarrow x\left(y+3\right)-\left(y+3\right)=3\\ \Rightarrow\left(x-1\right)\left(y+3\right)=3\)

Vì \(x,y\in Z\Rightarrow\left\{{}\begin{matrix}x-1,y+3\in Z\\x-1,y+3\inƯ\left(3\right)\end{matrix}\right.\)

Ta có bảng:

Vậy \(\left(x,y\right)\in\left\{\left(0;-6\right);\left(-2;-;\right);\left(2;0\right);\left(4;-2\right)\right\}\)

\(xy+3x-y=6\)

⇒ \(x\left(y+3\right)-\left(y+3\right)=3\)

⇒ \(\left(x-1\right)\left(y+3\right)=3\)

Đến đây em tự xét các trường hợp nha

=>6(x-7)=7(y-7) và x-y=-4

=>6x-42=7y-49 và x-y=-4

=>6x-7y=-7 và x-y=-4

=>x=-21 và y=-17

y \(\in\){6;7;8}

****

Ta có \(\dfrac{7-x}{13+y}=\dfrac{7}{13}\Rightarrow\dfrac{7-x}{7}=\dfrac{13+y}{13}\)

Áp dụng tính chất dãy tỉ số bằng nhau:

\(\dfrac{7-x}{7}=\dfrac{13+y}{13}=\dfrac{13+y-7+x}{13-7}=\dfrac{6+x+y}{6}=\dfrac{2022+6}{6}=338\)

\(\Rightarrow\left\{{}\begin{matrix}7-x=338\times7=2366\\13+y=338\times13=4394\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=-2359\\y=4381\end{matrix}\right.\)

Ta có \(\dfrac{7-x}{13+y}=\dfrac{7}{13}\Rightarrow\dfrac{7-x}{7}=\dfrac{13+y}{13}\)

Áp dụng tính chất dãy tỉ số bằng nhau:

\(\dfrac{7-x}{7}=\dfrac{13+y}{13}=\dfrac{13+y-7+x}{13-7}=\dfrac{6+x+y}{6}=\dfrac{2022+6}{6}=338\)

\(\Rightarrow\left\{{}\begin{matrix}7-x=338\times7=2366\\13+y=338\times13=4394\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=-2359\\y=4381\end{matrix}\right.\)

`4/7 - y xx 2=2/7`

`=> y xx 2= 4/7-2/7`

`=> y xx 2=2/7`

`=>y=2/7 : 2`

`=>y=2/7xx1/2`

`=>y=2/14`

`=>y=1/7`

4/7 -  y x 2 = 2/7

y x 2 = 4/7 - 2/7

y x 2 =    2/7

y = 2/7 : 2 = 1/7

a. \(k=\frac{y}{x}=2\)

b.

c.