Bài 1:

a, \(\frac{1}{x+1}+\frac{2}{x-1}=\frac{1+x^2}{x^2-1}\) (ĐKXĐ: x \(\ne\) \(\pm\) 1)

\(\Leftrightarrow\) \(\frac{x-1}{\left(x+1\right)\left(x-1\right)}+\frac{2\left(x+1\right)}{\left(x+1\right)\left(x-1\right)}=\frac{1+x^2}{\left(x+1\right)\left(x-1\right)}\)

\(\Rightarrow\) x - 1 + 2(x + 1) = 1 + x²

\(\Leftrightarrow\) x - 1 + 2x + 2 - 1 - x² = 0

\(\Leftrightarrow\) -x² + 3x = 0

\(\Leftrightarrow\) x(3 - x) = 0

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

Vậy S = {0; 3}

b, \(\frac{x-2}{x+2}-\frac{x}{x-2}=\frac{8}{x^2-4}\) (ĐKXĐ: x \(\ne\) \(\pm\) 2)

\(\Leftrightarrow\) \(\frac{\left(x-2\right)^2}{\left(x+2\right)\left(x-2\right)}-\frac{x\left(x+2\right)}{\left(x+2\right)\left(x-2\right)}=\frac{8}{\left(x+2\right)\left(x-2\right)}\)

\(\Rightarrow\) (x - 2)² - x(x + 2) = 8

\(\Leftrightarrow\) (x - 2)² - x(x + 2) - 8 = 0

\(\Leftrightarrow\) x² - 4x + 4 - x² - 2x - 8 = 0

\(\Leftrightarrow\) -6x - 4 = 0

\(\Leftrightarrow\) x = \(\frac{-2}{3}\) (TMĐKXĐ)

Vậy S = {\(\frac{-2}{3}\)}

c, \(\frac{1}{x}\) + \(\frac{2}{x-3}\) = \(\frac{1-5x}{x^2-3x}\) (ĐKXĐ: x \(\ne\) 0; x \(\ne\) 3)

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

\(\Rightarrow\) x - 3 + 2x = 1 - 5x

\(\Leftrightarrow\) 3x - 3 = 1 - 5x

\(\Leftrightarrow\) 3x + 5x = 1 + 3

\(\Leftrightarrow\) 8x = 4

\(\Leftrightarrow\) x = \(\frac{1}{2}\) (TMĐKXĐ)

Vậy S = {\(\frac{1}{2}\)}

Bài 2:

a, \(\frac{1}{x+2}=\frac{5}{2-x}+\frac{12+x}{x^2-4}\)

\(\Leftrightarrow\) \(\frac{1}{x+2}=\frac{-5}{x-2}+\frac{12+x}{\left(x-2\right)\left(x+2\right)}\)

\(\Leftrightarrow\) \(\frac{x-2}{\left(x+2\right)\left(x-2\right)}=\frac{-5\left(x+2\right)}{\left(x+2\right)\left(x-2\right)}+\frac{12+x}{\left(x+2\right)\left(x-2\right)}\)

\(\Rightarrow\) x - 2 = -5(x + 2) + 12 + x

\(\Leftrightarrow\) x - 2 = -5x - 10 + 12 + x

\(\Leftrightarrow\) x - 2 = -4x + 2

\(\Leftrightarrow\) x + 4x = 2 + 2

\(\Leftrightarrow\) 5x = 4

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

Vậy S = {\(\frac{4}{5}\)}

Chúc bn học tốt!! (Phần b hình như không có gì thì phải)

Bài 1:

1, \(\frac{2x-5}{x+5}=3\) (ĐKXĐ: x \(\ne\) -5)

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

\(\Rightarrow\) 2x - 5 = 3(x + 5)

\(\Leftrightarrow\) 2x - 5 = 3x + 15

\(\Leftrightarrow\) 2x - 3x = 15 + 5

\(\Leftrightarrow\) -x = 20

\(\Leftrightarrow\) x = -20 (TMĐKXĐ)

Vậy S = {-20}

2, \(\frac{4}{x+1}=\frac{3}{x-2}\) (ĐKXĐ: x \(\ne\) -1; x \(\ne\) 2)

\(\Leftrightarrow\) \(\frac{4\left(x-2\right)}{\left(x+1\right)\left(x-2\right)}=\frac{3\left(x+1\right)}{\left(x+1\right)\left(x-2\right)}\)

\(\Rightarrow\) 4(x - 2) = 3(x + 1)

\(\Leftrightarrow\) 4x - 8 = 3x + 3

\(\Leftrightarrow\) 4x - 3x = 3 + 8

\(\Leftrightarrow\) x = 11 (TMĐKXĐ)

Vậy S = {11}

3, \(\frac{5}{2x-3}=\frac{1}{x-4}\) (ĐKXĐ: x \(\ne\) \(\frac{3}{2}\); x \(\ne\) 4)

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

\(\Rightarrow\) 5(x - 4) = 2x - 3

\(\Leftrightarrow\) 5x - 20 = 2x - 3

\(\Leftrightarrow\) 5x - 2x = -3 + 20

\(\Leftrightarrow\) 3x = 17

\(\Leftrightarrow\) x = \(\frac{17}{3}\) (TMĐKXĐ)

Vậy S = {\(\frac{17}{3}\)}

Bài 2:

1, \(\frac{1}{x-1}+\frac{2}{x+1}=\frac{5x-3}{x^2-1}\) (ĐKXĐ: x \(\ne\) \(\pm\) 1)

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

\(\Rightarrow\) x + 1 + 2(x - 1) = 5x - 3

\(\Leftrightarrow\) x + 1 + 2x - 2 = 5x - 3

\(\Leftrightarrow\) 3x - 1 = 5x - 3

\(\Leftrightarrow\) 3x - 5x = -3 + 1

\(\Leftrightarrow\) -2x = -2

\(\Leftrightarrow\) x = 1 (KTM)

\(\Rightarrow\) Pt vô nghiệm

Vậy S = \(\varnothing\)

2, \(\frac{x+2}{x-2}-\frac{1}{x}=\frac{2}{x^2-2x}\) (ĐKXĐ: x \(\ne\) 2; x \(\ne\) 0)

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

\(\Rightarrow\) x(x + 2) - x + 2 = 2

\(\Leftrightarrow\) x² + 2x - x + 2 = 2

\(\Leftrightarrow\) x² + x = 2 - 2

\(\Leftrightarrow\) x² + x = 0

\(\Leftrightarrow\) x(x + 1) = 0

\(\Leftrightarrow\) x = 0 hoặc x + 1 = 0

\(\Leftrightarrow\) x = 0 và x = -1

Ta có: x = 0 KTM đkxđ

\(\Rightarrow\) x = -1

Vậy S = {-1}

3, \(\frac{5}{x-3}-\frac{3}{x+3}=\frac{3x}{x^2-9}\) (ĐKXĐ: x \(\ne\) \(\pm\) 3)

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

\(\Rightarrow\) 5(x + 3) - 3(x - 3) = 3x

\(\Leftrightarrow\) 5x + 15 - 3x + 9 = 3x

\(\Leftrightarrow\) 2x + 24 = 3x

\(\Leftrightarrow\) 2x - 3x = 24

\(\Leftrightarrow\) -x = 24

\(\Leftrightarrow\) x = -24 (TMĐKXĐ)

Vậy S = {-24}

Chúc bn học tốt!!

Mình tính mãi vẫn có chỗ sai, mong bạn thông cảm!!

a/ 4x + 20 = 0

⇔4x = -20

⇔x = -5

Vậy phương trình có tập nghiệm S = {-5}

b/ 2x – 3 = 3(x – 1) + x + 2

⇔ 2x-3 = 3x -3+x+2

⇔2x – 3x = -3+2+3

⇔-2x = 2

⇔x = -1

Vậy phương trình có tập nghiệm S = {-1}
 

câu tiếp theo

a/ (3x – 2)(4x + 5) = 0

3x – 2 = 0 hoặc 4x + 5 = 0

Vậy phương trình có tập nghiệm S= {-5/4,3/2}

b/ 2x(x – 3) – 5(x – 3) = 0

=> (x – 3)(2x -5) = 0

=> x – 3 = 0 hoặc 2x – 5 = 0

* x – 3 = 0 => x = 3

* 2x – 5 = 0 => x = 5/2

Vậy phương trình có tập nghiệm S = {0, 5/2}

b1

a. 4x+ 20=0 <=> 4x= -20 <=> x= -20/4 <=> x= -5

b. 2x- 3= 3(x- 1)+ x+ 2 <=> 2x- 3= 3x- 3+ x+ 2

<=> 2x- 3= 4x- 1 <=> 2x- 4x= -1+ 3 <=> -2x= 2

<=> x= 2/-2 <=> x= -1

b2

a. (3x- 2)(4x+ 5)= 0

<=>\(\orbr{\begin{cases}3x-2=0\\4x+5=0\end{cases}\Leftrightarrow\orbr{\begin{cases}3x=2\\4x=-5\end{cases}}}\)

<=>\(\orbr{\begin{cases}x=\frac{2}{3}\\x=-\frac{5}{4}\end{cases}}\)

b. 2x(x- 3)- 5(x- 3)= 0

<=> (x- 3)(2x- 5)= 0

<=> \(\orbr{\begin{cases}x-3=0\\2x-5=0\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=3\\2x=5\end{cases}}\)

<=> \(\orbr{\begin{cases}x=3\\x=\frac{5}{2}\end{cases}}\)

3(2x+y)-2(3x-2y)=3.19-11.2

6x+3y-6x+4y=57-22

7y=35

y=5

thay vào :

2x+y=19

2x+5=19

2x=14

x=7

2/ x²+21x-1x-21=0

x(x+21)-1(x+21)=0

(x+21)(x-1)=0

TH1 x+21=0

x=-21

TH2 x-1=0

x=1

vậy x = {-21} ; {1}

3/ x⁴-16x²-4x²+64=0

x²(x²-16)-4(x²-16)=0

(x²-16)-(x²-4)=0

TH1 x²-16=0

x²=16

<=>x=4;-4

TH2 x²-4=0

x²=4

x=2;-2

Bài 1 : 

\(\hept{\begin{cases}2x+y=19\\3x-2y=11\end{cases}\Leftrightarrow\hept{\begin{cases}4x+2y=38\\3x-2y=11\end{cases}\Leftrightarrow\hept{\begin{cases}7x=49\\2x+y=19\end{cases}}}}\)

\(\Leftrightarrow\hept{\begin{cases}x=7\\2x+y=19\end{cases}}\)Thay vào x = 7 vào pt 2 ta được : 

\(14+y=19\Leftrightarrow y=5\)Vậy hệ pt có một nghiệm ( x ; y ) = ( 7 ; 5 )

Bài 2 : 

\(x^2+20x-21=0\)

\(\Delta=400-4\left(-21\right)=400+84=484\)

\(x_1=\frac{-20-22}{2}=-24;x_2=\frac{-20+22}{2}=1\)

Bài 3 : Đặt \(x^2=t\left(t\ge0\right)\)

\(t^2-20t+64=0\)

\(\Delta=400+4.64=656\)

\(t_1=\frac{20+4\sqrt{41}}{2}\left(tm\right);t_2=\frac{20-4\sqrt{41}}{2}\left(ktm\right)\)

Theo cách đặt : \(x^2=\frac{20+4\sqrt{41}}{2}\Rightarrow x=\sqrt{\frac{20+4\sqrt{41}}{2}}=\frac{\sqrt{20\sqrt{2}+4\sqrt{82}}}{2}\)

\(\hept{\begin{cases}2x+y=19\\3x-2y=11\end{cases}\hept{\begin{cases}6x+3y=57\\6x-4y=22\end{cases}\hept{\begin{cases}7y=35\\3x-2y=11\end{cases}}}}\)

\(\hept{\begin{cases}y=5\\3x-2.5=11\end{cases}\hept{\begin{cases}y=5\\3x=21\end{cases}\hept{\begin{cases}y=5\\x=7\end{cases}}}}\)

\(a=1,b=20;c=-21\)

\(\Delta=\left(20\right)^2-\left(4.1.-21\right)=484\)

\(\sqrt{\Delta}=\sqrt{484}=22\)

\(x_1=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-20+22}{2}=1\left(TM\right)\)

\(x_2=\frac{-b-\sqrt{\Delta}}{2a}=-21\left(TM\right)\)

\(3,x^4-20x^2+64=0\)

đặt \(x^2=a\)ta có pt

\(a^2-20a+64=0\)

\(a=1;b=-20;c=64\)

\(\Delta=\left(-20\right)^2-\left(4.1.64\right)=144\)

\(\sqrt{\Delta}=12\)

\(a_1=\frac{-b+\sqrt{\Delta}}{2a}=16\left(TM\right)\)

\(a_2=\frac{-b-\sqrt{\Delta}}{2a}=4\left(TM\right)\)

\(< =>x_1=\sqrt{16}=4\left(TM\right)\)

\(x_2=\sqrt{4}=2\left(TM\right)\)

vậy bộ n⁰ của pt là (\(4;2\))

a) | 2x - 1 | + | 3 - x | = 3

<=> | 2x - 1 | + | x - 3 | = 3

+) Với x < 1/2

pt <=> -( 2x - 1 ) - ( x - 3 ) = 3

<=> -2x + 1 - x + 3 = 3

<=> -3x = -1 <=> x = 1/3 (tm)

+) Với 1/2 ≤ x < 3

pt <=> 2x - 1 - ( x - 3 ) = 3

<=> 2x - 1 - x + 3 = 3

<=> x = 1 (tm)

+) Với x ≥ 3

pt <=> 2x - 1 + x - 3 = 3

<=> 3x = 7 <=> x = 7/3 (ktm)

Vậy ...

a, \(\left|2x-1\right|+\left|3-x\right|\ge2x-1+3-x=x+2\)

\(\Rightarrow\left|x+2\right|=3\Rightarrow\orbr{\begin{cases}x=1\\x=-5\end{cases}}\)

Vậy tập nghiệm của phương trình là S = { -5 ; 1 } 

b, \(x^3-5x^2-4x+20=0\)

\(\Leftrightarrow x\left(x^2-4\right)-5\left(x^2-4\right)=0\)

\(\Leftrightarrow\left(x\pm2\right)\left(x-5\right)=0\Rightarrow\orbr{\begin{cases}x=\pm2\\x=5\end{cases}}\)

Vậy tập nghiệm của phương trình là S = { -2 ; 2 ; 5 } 

Xét \(x< \frac{1}{2}\Rightarrow PT\Leftrightarrow1-2x+3-x=3\Leftrightarrow x=\frac{1}{3}\)

với \(\frac{1}{2}\le x\le3\Rightarrow PT\Leftrightarrow2x-1+3-x=3\Leftrightarrow x=1\)

với \(x>3,PT\Leftrightarrow2x-1+x-3=3\Leftrightarrow x=\frac{7}{3}\text{loại}\)

b.\(PT\Leftrightarrow\left(x-5\right)\left(x-2\right)\left(x+2\right)=0\Leftrightarrow\orbr{\begin{cases}x=5\\x=\pm2\end{cases}}\)

a, \(\dfrac{1}{2}\sqrt{x-5}-\sqrt{4x-20+3}=0\left(dkxd:x\ge5\right)\)

\(< =>\dfrac{\sqrt{x-5}}{2}=\sqrt{4x-17}\)

\(< =>\dfrac{x-5}{4}=4x-17\)

\(< =>x-5=16x-68\)

\(< =>15x=68-5=63\)

\(< =>x=\dfrac{63}{15}=\dfrac{21}{5}\)(ktm)

b, \(\sqrt{2x+1}-2\sqrt{x}+1=0\left(dkxd:x\ge0\right)\)

\(< =>\sqrt{2x+1}+1=2\sqrt{x}\)

\(< =>2x+1+1+2\sqrt{2x+1}=4x\)

\(< =>2x-2\sqrt{2x+1}-2=0\)

\(< =>2x+1-2\sqrt{2x+1}+1-4=0\)

\(< =>\left(\sqrt{2x+1}-1\right)^2=4\)

\(< =>\left\{{}\begin{matrix}\sqrt{2x+1}-1=2\\\sqrt{2x+1}-1=-2\end{matrix}\right.\)

\(< =>\left\{{}\begin{matrix}\sqrt{2x+1}=3\\\sqrt{2x+1}=-1\left(loai\right)\end{matrix}\right.\)

\(< =>2x+1=9< =>2x=8< =>x=4\)(tmdk)

Bài 1: 

a: Ta có: 4x+20=0

nên 4x=-20

hay x=-5

b: Ta có: \(\left(x^2-2x+1\right)-4=0\)

\(\Leftrightarrow\left(x-1\right)^2=4\)

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

c: Ta có: \(\dfrac{x+3}{x+1}+\dfrac{x-2}{x}=2\)

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

Suy ra: \(x^2+3x+x^2-2x+x-2=2x^2+2x\)

\(\Leftrightarrow4x-2-2x=0\)

\(\Leftrightarrow2x=2\)

hay \(x=1\left(nhận\right)\)

Bài 2: 

Ta có: \(3x-\left(7x+2\right)>5x+4\)

\(\Leftrightarrow3x-7x-2-5x-4>0\)

\(\Leftrightarrow-9x>6\)

hay \(x< -\dfrac{2}{3}\)

a) \(5x - 30 = 0\)

\(5x = 0 + 30\)     

\(5x = 30\)

\(x = 30:5\)

\(x = 6\)      

Vậy phương trình có nghiệm \(x = 6\).

b) \(4 - 3x = 11\)

\( - 3x = 11 - 4\)

\( - 3x =  7\)

\(x = \left( { 7} \right):\left( { - 3} \right)\)

\(x = \dfrac{-7}{3}\)

Vậy phương trình có nghiệm \(x = \dfrac{7}{3}\).

c) \(3x + x + 20 = 0\)               

\(4x + 20 = 0\)

\(4x = 0 - 20\)

\(4x =  - 20\)

\(x = \left( { - 20} \right):4\)

\(x =  - 5\)   

Vậy phương trình có nghiệm \(x =  - 5\).

d) \(\dfrac{1}{3}x + \dfrac{1}{2} = x + 2\)

\(\dfrac{1}{3}x - x = 2 - \dfrac{1}{2}\)

\(\dfrac{{ - 2}}{3}x = \dfrac{3}{2}\)

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

\(x = \dfrac{{ - 9}}{4}\)

Vậy phương trình có nghiệm \(x = \dfrac{{ - 9}}{4}\).

a: 3x-15=0

nên 3x=15

hay x=5

b: 4x+20=0

nên 4x=-20

hay x=-5

c: -5x-20=0

nên -5x=20

hay x=-4