Làm sao 2 ẩn mà chỉ có 1 phương trình mà giải đc nhỉ ??

Thầy cho bọn tớ thế !

Ta có : \(\frac{6}{8}=\frac{3}{4}\)

\(\frac{x}{y}=\frac{3}{4}\)

\(\Rightarrow4x=3y\)

\(\Rightarrow x=3;y=4\)

a) Ko tìm được gt nào của x vì \(\left|x\right|\ge0\)

d)=> x - 3,5 = 5 hoặc x - 3,5 = -5

=> x = 5 + 3,5 hoặc x = -5 + 3,5

=> x = 8,5 hoặc x = -1.5

e: =>|x+0,75|=1,4

=>x+0,75=1,4 hoặc x+0,75=-1,4

=>x=-2,15 hoặc x=0,65

g: =>|x-2|=1/2

=>x-2=1/2 hoặc x-2=-1/2

=>x=5/2 hoặc x=3/2

a) \(x\cdot3\dfrac{1}{4}+\left(-\dfrac{7}{6}\right)\cdot x-1\dfrac{2}{3}=\dfrac{5}{12}\)

\(\Rightarrow\dfrac{3}{4}x-\dfrac{7}{6}x-\dfrac{2}{3}=\dfrac{5}{12}\)

\(\Leftrightarrow9x-14x-8=5\)

\(\Leftrightarrow-5x-8=5\)

\(\Leftrightarrow-5x=5+8\)

\(\Leftrightarrow-5x=13\)

\(\Rightarrow x=-\dfrac{13}{5}\)

Vậy \(x=-\dfrac{13}{5}\)

b) \(5\dfrac{8}{17}:x+\left|2x-\dfrac{3}{4}\right|=-\dfrac{7}{4}\)

\(\Rightarrow5\dfrac{8}{17}:x+\left|2x-\dfrac{3}{4}\right|=-\dfrac{7}{4}\left(đk:x\ne0\right)\)

\(\Leftrightarrow\dfrac{93}{17}\cdot\dfrac{1}{x}+\left|2x-\dfrac{3}{4}\right|=-\dfrac{7}{4}\)

\(\Leftrightarrow\dfrac{93}{17x}+\left|2x-\dfrac{3}{4}\right|=-\dfrac{7}{4}\)

\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{93}{17x}+2x-\dfrac{3}{4}=-\dfrac{7}{4}\left(đk:2x-\dfrac{3}{4}\ge0\right)\\\dfrac{93}{17x}-\left(2x-\dfrac{3}{4}\right)=-\dfrac{7}{4}\left(đk:2x-\dfrac{3}{4}< 0\right)\end{matrix}\right.\)

đến đây bạn giải tiếp nhé

c) \(\left(x+\dfrac{1}{2}\right)\cdot\left(\dfrac{2}{3}-2x\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=0\\\dfrac{2}{3}-2x=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0-\dfrac{1}{2}\\2x=0+\dfrac{2}{3}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{2}\\x=\dfrac{2}{3}:2\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=-\dfrac{1}{2}\\x=\dfrac{1}{3}\end{matrix}\right.\)

Vậy \(x_1=-\dfrac{1}{2};x_2=\dfrac{1}{3}\)

b: =>x/23=1+3/4+4/7=65/28

=>x=23*65/28=1495/28

c: =>3/5:x=3/5-1/4-1/2=9/40

=>x=3/5:9/40=8/3

43/30

1/16

10/21

5/3

43/30

1/16

10/21

5/3

Bài 1: Tính

a, 5/6 + 3/5=40/30

b, 11/16 - 5/8=1/16

c, 5/9 x 6/7=30/63

d, 5/4 : 3/4=5/3

giúp me

\(a,\Leftrightarrow-\dfrac{1}{2}x=\dfrac{1}{4}\Leftrightarrow x=-\dfrac{1}{2}\\ b,\Leftrightarrow\dfrac{1}{6}:x=\dfrac{1}{2}+\dfrac{1}{3}=\dfrac{5}{6}\Leftrightarrow x=\dfrac{1}{6}:\dfrac{5}{6}=\dfrac{1}{5}\\ c,\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{5}=3\\x+\dfrac{1}{5}=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{14}{5}\\x=-\dfrac{16}{5}\end{matrix}\right.\)

\(d,\Leftrightarrow\left(x+\dfrac{1}{2}\right)^2=\dfrac{22}{9}-\dfrac{7}{3}=\dfrac{1}{9}\\ \Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=\dfrac{1}{3}\\x+\dfrac{1}{2}=-\dfrac{1}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{6}\\x=-\dfrac{5}{6}\end{matrix}\right.\\ e,\Leftrightarrow2\left|x\right|=2-\dfrac{1}{2}=\dfrac{3}{2}\\ \Leftrightarrow\left[{}\begin{matrix}2x=\dfrac{3}{2}\\2x=-\dfrac{3}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{4}\\x=-\dfrac{3}{4}\end{matrix}\right.\)

\(f,\Leftrightarrow\left|x+\dfrac{1}{2}\right|=1+\dfrac{1}{6}=\dfrac{7}{6}\\ \Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=\dfrac{7}{6}\\x+\dfrac{1}{2}=-\dfrac{7}{6}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=-\dfrac{5}{3}\end{matrix}\right.\)

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 \(x\in\left\{\dfrac{3}{4};-\dfrac{3}{4}\right\}\)

a: Bạn ghi lại đề nha bạn

b: \(30\left(x+2\right)-6\left(x-5\right)-24x=100\)

=>\(30x+60-6x+30-24x=100\)

=>\(\left(30x-6x-24x\right)+\left(60+30\right)=100\)

=>0x=100-90=10(vô lý)

c: \(\left(x-7\right)\left(x+3\right)< 0\)

TH1: \(\left\{{}\begin{matrix}x-7>0\\x+3< 0\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}x>7\\x< -3\end{matrix}\right.\)

=>\(x\in\varnothing\)

TH2: \(\left\{{}\begin{matrix}x-7< 0\\x+3>0\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}x< 7\\x>-3\end{matrix}\right.\)

=>-3<x<7

mà x nguyên

nên \(x\in\left\{-2;-1;0;1;2;3;4;5;6\right\}\)

d: -1<2x-1<4

=>\(-1+1< 2x< 4+1\)

=>0<2x<5

=>0<x<2,5

mà x nguyên

nên \(x\in\left\{1;2\right\}\)

Cái này dễ mà bn

Ta có:\(A=\frac{x+2}{x+3}-\frac{5}{x^2+x-6}+\frac{1}{2-x}\left(ĐK:x\ne2;-3\right)\)

    \(\Leftrightarrow A=\frac{x+2}{x+3}-\frac{5}{\left(x+3\right)\left(x-2\right)}-\frac{1}{x-2}\)

    \(\Leftrightarrow A=\frac{x^2-4-5-x-3}{\left(x+3\right)\left(x-2\right)}\)

     \(\Leftrightarrow A=\frac{x^2-x-12}{\left(x+3\right)\left(x-2\right)}=\frac{x+4}{x-2}\)

\(A=\frac{x+2}{x+3}-\frac{5}{x^2+x-6}+\frac{1}{2-x}\)

\(\Leftrightarrow A=\frac{x}{\left(2+3\right)}^2-\frac{5}{x^3-6}+\left(2-x\right)\)

\(\Leftrightarrow A=\frac{x}{5}^2-\frac{5}{x^3-6}+\left(2-x\right)\)

Ps: Không chắc đâu nhé! Thánh đây mới lớp 6 thôi

:v công nhận năm lớp 6 tôi trẩu vl!

ĐK: \(x\ne2;x\ne-3\)

\(A=\frac{x+2}{x+3}-\frac{5}{x^2+x-6}+\frac{1}{2-x}\)

\(=\frac{x+2}{x+3}-\frac{5}{\left(x+3\right)\left(x-2\right)}-\frac{1}{x-2}\)

\(=\frac{\left(x+2\right)\left(x-2\right)-5-x-3}{\left(x+3\right)\left(x-2\right)}\)

\(=\frac{x^2-4-5-x-3}{\left(x+3\right)\left(x+2\right)}=\frac{x^2-x-12}{\left(x+3\right)\left(x+2\right)}=\frac{\left(x-4\right)\left(x+3\right)}{\left(x+3\right)\left(x+2\right)}=\frac{x-4}{x+2}\)