a: \(=\dfrac{7}{5}\cdot\dfrac{15}{49}-\dfrac{12+10}{15}:\dfrac{11}{5}\)

\(=\dfrac{3}{7}-\dfrac{22}{15}\cdot\dfrac{5}{11}=\dfrac{3}{7}-\dfrac{2}{3}=\dfrac{9-14}{21}=\dfrac{-5}{21}\)

b: =>2,8x-32=-60

=>2,8x=-28

hay x=-10

Câu 1 : 

Đk: \(x\ge1\) 

\(\sqrt{x-1}+\sqrt{2x-1}=5\\ \Leftrightarrow x-1+2\sqrt{\left(x-1\right)\left(2x-1\right)}+2x-1=25\\ \Leftrightarrow2\sqrt{2x^2-3x+1}=27-3x\\ \)

\(\Leftrightarrow\begin{cases}27-3x\ge0\\4\left(2x^2-3x+1\right)=9x^2-162x+729\end{cases}\) \(\Leftrightarrow\begin{cases}x\le9\\x^2-150x+725=0\end{cases}\)

\(\Leftrightarrow\begin{cases}x\le9\\x=145hoặcx=5\end{cases}\)

với x= 5 thoản mãn điều kiện, x=145 loại

Vậy \(S=\left\{5\right\}\)

vĐk: \(� \geq 1\) 

\(\sqrt{� - 1} + \sqrt{2 � - 1} = 5 \Leftrightarrow � - 1 + 2 \sqrt{\left(\right. � - 1 \left.\right) \left(\right. 2 � - 1 \left.\right)} + 2 � - 1 = 25 \Leftrightarrow 2 \sqrt{2 �^{2} - 3 � + 1} = 27 - 3 �\)

\(\Leftrightarrow \left{\right. 27 - 3 � \geq 0 \\ 4 \left(\right. 2 �^{2} - 3 � + 1 \left.\right) = 9 �^{2} - 162 � + 729\) \(\Leftrightarrow \left{\right. � \leq 9 \\ �^{2} - 150 � + 725 = 0\)

\(\Leftrightarrow \left{\right. � \leq 9 \\ � = 145 ℎ � ặ � � = 5\)

với x= 5 thoản mãn điều kiện, x=145 loại

Vậy \(� = \left{\right. 5 \left.\right}\)

a: \(\Leftrightarrow2x^2+4-x^2+\dfrac{3}{2}=-3+4x^2-\dfrac{4}{3}x^2+1\)

\(\Leftrightarrow x^2+\dfrac{11}{2}=\dfrac{8}{3}x^2-2\)

\(\Leftrightarrow x^2\cdot\dfrac{-5}{3}=-\dfrac{15}{2}\)

\(\Leftrightarrow x^2=\dfrac{9}{2}\)

hay \(x\in\left\{\dfrac{3\sqrt{2}}{2};-\dfrac{3\sqrt{2}}{2}\right\}\)

b: \(\Leftrightarrow\left|x\right|-4-2+\left|x\right|-\dfrac{1}{3}\left|x\right|+5=0\)

\(\Leftrightarrow\left|x\right|\cdot\dfrac{5}{3}=1\)

hay \(x\in\left\{\dfrac{3}{5};-\dfrac{3}{5}\right\}\)

x = 4 ; -5 : -7

a) x=7-3=4

b)x=-5

c)x=2-9=-7

vd câu 1:
ta có x-y=4 =>x=4+y
ta có pt:
4+y/y-2=3/2
=>8+2y=3y-6
=>-y=-14
=>y=14
=>x=4+y=4+14=18
các bài khác cũng tương tự thôi bạn

dấu chéo có nghĩa là phân số hí

sao ko ai tra loi het z

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

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

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

\(-2x-6,7=-x\)

\(-2x-x=6,7\)

\(-3x=6,7\)

\(x=-\frac{67}{30}\)

Vậy \(x=-\frac{67}{30}\)

=>3x-3/2-5x-3=-x+1/5
=>-2x+x=1/5+9/2
=>-x=47/10
=>x=-47/10