a)   | x + 10 | - ( 5 - 3x ) = ( 4x - 10 ) - ( x - 5 )

=>                   | x + 10 | = ( 5 - 3x ) + ( 4x - 10 ) - ( x - 5 )

=>                   | x + 10 | = 5 - 3x + 4x - 10 - x + 5

=>                   | x +10 | = 0

=>                     x + 10 = 0

=>                      x = -10

              Vậy...

b) Làm tương tự 

Kết quả : | 3x + 21 | = -10  ( vô lí)       ( vì |3x+21| >= 0 mà -10<0)

Vậy không tìm được x thỏa mãn bài toán

Các bn giúp mình với mình đang cần gấp

nhiều quá bạn ơi , mk nghĩ bạn nên tách ra rồi hãy đăng lên

Bài 1:

16:

=>15-30x-8+8x=4x-9

=>-22x+7=4x-9

=>-26x=-16

=>x=8/13

15: \(\Leftrightarrow12x-6+12-4x=10-6x\)

=>8x+6=10-6x

=>14x=4

=>x=2/7

14: \(\Leftrightarrow12x-18+9-15x=8x-9\)

=>-3x-9=8x-9

=>x=0

13: \(\Leftrightarrow10x+15x-10=25-10x\)

=>25x-10=25-10x

=>35x=35

=>x=1

12: \(\Leftrightarrow15x-18-4x+10=11x-10\)

=>11x-8=11x-10(loại)

c: =>\(\dfrac{2x-1}{\left(x+5\right)\left(x-1\right)}+\dfrac{x-2}{\left(x-1\right)\left(x-9\right)}=\dfrac{3x-12}{\left(x-9\right)\left(x+5\right)}\)

=>(2x-1)(x-9)+(x-2)(x+5)=(3x-12)(x-1)

=>2x^2-19x+9+x^2+3x-10=3x^2-15x+12

=>-16x-1=-15x+12

=>-x=13

=>x=-13

1)6x-8=3x+1

6x-3x=1+8

3x=9

x=3

Vậy x=3

2: 12-10x=25-30x

=>20x=13

=>x=13/20

3: \(3\left(2x+3\right)-2\left(4x-5\right)=10x+21\)

=>6x+9-8x+10=10x+21

=>10x+21=-2x+19

=>12x=-2

=>x=-1/6

4: \(\Leftrightarrow25x-15-6x+12=11-5x\)

=>19x-3=11-5x

=>24x=14

=>x=7/12

5: \(\Leftrightarrow8-12x-5+10x=4-6x\)

=>4-6x=-2x+3

=>-4x=-1

=>x=1/4

6: \(\Leftrightarrow32x-24-6+9x=13-40x\)

=>41x-30=13-40x

=>81x=43

=>x=43/81

7: \(\Leftrightarrow10x-5+20x=5x-11\)

=>30x-5=5x-11

=>25x=-6

=>x=-6/25

a \(\dfrac{1}{x-y}+\dfrac{2}{x+y}+\dfrac{3x}{y^2-x^2}\)

\(=\dfrac{x+y+2x-2y-3x}{\left(x-y\right)\left(x+y\right)}=\dfrac{-y}{\left(x-y\right)\left(x+y\right)}\)

b: \(\dfrac{1}{x-2}+\dfrac{1}{x+2}-\dfrac{4x-4}{x^2-4}\)

\(=\dfrac{x+2+x-2-4x+4}{\left(x-2\right)\left(x+2\right)}=\dfrac{-2x+4}{\left(x-2\right)\left(x+2\right)}\)

=-2/x+2

c: \(\dfrac{x+1}{x+3}-\dfrac{x-1}{3-x}+\dfrac{2x-2x^2}{x^2-9}\)

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

\(=\dfrac{x^2-2x-3+x^2+2x-3+2x-2x^2}{\left(x+3\right)\left(x-3\right)}\)

\(=\dfrac{2x-6}{\left(x+3\right)\left(x-3\right)}=\dfrac{2}{x+3}\)

\(\sqrt{-x^2+4x+21}-\sqrt{-x^2+3x+10}=\sqrt{-\left(x^2+4x+4\right)+25}-\)

\(\sqrt{-\left(x^2+3x+\frac{9}{4}\right)+\frac{49}{4}}\ge\sqrt{25}-\sqrt{\frac{49}{4}}=5-\frac{7}{2}=\frac{3}{2}\)

\(\Rightarrow GTNN\) của y = \(\frac{3}{2}\)

ĐKXĐ: \(-2\le x\le5\)

Ta có \(\left(-x^2+4x+21\right)-\left(-x^2+3x+10\right)=x+11>0\) \(\forall x\in\left[-2;5\right]\)

\(\Rightarrow\sqrt{-x^2+4x+21}>\sqrt{-x^2+3x+10}\Rightarrow y>0\)

\(\Rightarrow y^2=\left(\sqrt{\left(7-x\right)\left(x+3\right)}-\sqrt{\left(5-x\right)\left(x+2\right)}\right)^2\)

\(\Rightarrow y^2=-2x^2+7x+31-2\sqrt{\left(x+2\right)\left(7-x\right)\left(x+3\right)\left(5-x\right)}\)

\(\Rightarrow y^2=-x^2+5x+14-x^2+2x+15-2\sqrt{\left(x+2\right)\left(7-x\right)\left(x+3\right)\left(5-x\right)}+2\)

\(\Rightarrow y^2=\left(x+2\right)\left(7-x\right)-2\sqrt{\left(x+2\right)\left(7-x\right)\left(x+3\right)\left(5-x\right)}+\left(x+3\right)\left(5-x\right)+2\)

\(\Rightarrow y^2=\left(\sqrt{\left(x+2\right)\left(7-x\right)}-\sqrt{\left(x+3\right)\left(5-x\right)}\right)^2+2\ge2\)

\(\Rightarrow y_{min}=\sqrt{2}\) khi \(\sqrt{\left(x+2\right)\left(7-x\right)}=\sqrt{\left(x+3\right)\left(5-x\right)}\Rightarrow x=\frac{1}{3}\)

a, \(\left(4x-10\right)\left(24+3x\right)=0\)

⇔\(\left[{}\begin{matrix}4x-10=0\\24+3x=0\end{matrix}\right.\)

⇔\(\left[{}\begin{matrix}4x=10\\3x=-24\end{matrix}\right.\)

⇔\(\left[{}\begin{matrix}x=\frac{5}{2}\\x=-8\end{matrix}\right.\)

Vậy...

b,\(7x-21+x\left(x-3\right)=0\)

⇔\(7\left(x-3\right)+x\left(x-3\right)=0\)

⇔\(\left(7+x\right)\left(x-3\right)=0\)

⇔\(\left[{}\begin{matrix}7+x=0\\x-3=0\end{matrix}\right.\)

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

Vậy...

c,Mình bận quá.Xin lỗi mình xin không làm!

Gợi ý:

Phân tích vế trái sang hằng đẳng thức số 3 rồi tính nhé!

a) Ta có: \(\left(4x-10\right)\left(24+3x\right)=0\)

\(\Leftrightarrow6\left(2x-5\right)\left(8+x\right)=0\)

mà 6≠0

nên \(\left[{}\begin{matrix}2x-5=0\\8+x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=5\\x=-8\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{5}{2}\\x=-8\end{matrix}\right.\)

Vậy: \(S=\left\{\frac{5}{2};-8\right\}\)

b) Ta có: \(7x-21+x\left(x-3\right)=0\)

\(\Leftrightarrow7\left(x-3\right)+x\left(x-3\right)=0\)

\(\Leftrightarrow\left(x-3\right)\left(7+x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\7+x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-7\end{matrix}\right.\)

Vậy: S={3;-7}

c) Ta có: \(x^2-1=2x\left(x+1\right)\)

\(\Leftrightarrow\left(x-1\right)\left(x+1\right)-2x\left(x+1\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(x-2x-1\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(-x-1\right)=0\)

\(\Leftrightarrow-\left(x+1\right)^2=0\)

\(\Leftrightarrow x+1=0\)

hay x=-1

Vậy: S={-1}

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

⇔\(\left(x+1\right)\left(x-1\right)=2x\left(x+1\right)\)

⇔\(\left(x+1\right)\left(x-1\right)-2x\left(x+1\right)=0\)

⇔\(\left(x+1\right)\left(-x-1\right)=0\)

⇔\(\left[{}\begin{matrix}x+1=0\\-x-1=0\end{matrix}\right.\)

⇔\(\left[{}\begin{matrix}x=-1\\x=-1\end{matrix}\right.\)

Vậy...

Nhìu quá bạn ơi

nhiều vậy ai mà làm dc bạn ơi

làm hai câu ba câu cũng được

a) xy - x - y = 10 => (xy - x) - (y - 1) = 11 => (x - 1)(y - 1) = 11 => Tự bạn giải tiếp nha

b) xy + 3x - 6y = 21 => (xy + 3x) - (6y + 18) = 3 => (x - 6)(y + 3) = 3 => Tự bạn giải tiếp nha

c) xy + 4x - 3y =12 => (xy + 4x) - (3y + 12) = 0 => (x - 3)(y + 4) = 0 => x = 3 hoặc y = -4

a,xy-x-y=10

=>x(y-1)-y+1=10+1

=>x(y-1)-1(y-1)=11

=>(x-1)(y-1)=11

=>x-1 va y-1 la uoc cua 11

................

hai y con lai lam giong nhu vay 

a) -12+x=5x-20

-12+x  -5x = -20

-12+ ( -4x) = -20

-4x= -20-(-12)

-4x=-8

x= -8: (-4)

x= 2

Vậy....

Ko chắc nha

b) 4x-10=15-x

4x-10 +x=15

5x -10=15

5x= 15+10

5x= 25

x=25:5

x=5 

Vậy...

c) 7x-4=20+3x

7x -4 - 3x= 20

4x -4= 20

4x= 20+4

4x= 24

x= 24:4

x=6

Vậy...