Yêu cầu đề bài là gì bạn nên ghi đầy đủ ra nhé. Và nên viết đề bằng công thức toán để mọi người hiểu đề của bạn hơn.

a: ĐKXĐ: \(a\notin\left\{3;-3\right\}\)

\(\dfrac{a}{a-3}-\dfrac{3}{a+3}\)

\(=\dfrac{a\left(a+3\right)-3\left(a-3\right)}{\left(a-3\right)\left(a+3\right)}\)

\(=\dfrac{a^2+3a-3a+9}{\left(a-3\right)\left(a+3\right)}=\dfrac{a^2+9}{a^2-9}\)

b: ĐKXĐ: x<>0

\(\dfrac{1}{2x}+\dfrac{2}{x^2}\)

\(=\dfrac{x+2\cdot2}{2x^2}=\dfrac{x+4}{2x^2}\)

c: ĐKXĐ: \(x\notin\left\{1;-1\right\};b< >0\)

\(\dfrac{4}{x^2-1}-\dfrac{2}{3b}\)

\(=\dfrac{4\cdot3b-2\left(x^2-1\right)}{3b\left(x^2-1\right)}\)

\(=\dfrac{12b-2x^2+2}{3b\left(x^2-1\right)}\)

2.a) \(8x^2-4x=0\Rightarrow4x\left(2x-1\right)=0\\ \Rightarrow\left[{}\begin{matrix}4x=0\\2x-1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{2}\end{matrix}\right.\)

b) \(5x\left(x-3\right)+7\left(x-3\right)=0\Rightarrow\left(x-3\right)\left(5x+7\right)=0\\ \Rightarrow\left[{}\begin{matrix}x-3=0\\5x+7=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=3\\x=-1.4\end{matrix}\right.\)

c) \(2x^2=x\Rightarrow2x^2-x=0\Rightarrow x\left(2x-1\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=0\\2x-1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=0.5\end{matrix}\right.\)

d) \(x^3=x^5\Rightarrow x^3-x^5=0\Rightarrow x^3\left(1-x^2\right)=0\\ \Rightarrow x^3\left(1-x\right)\left(1+x\right)=0\Rightarrow\left[{}\begin{matrix}x^3=0\\1-x=0\\1+x=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=1\\x=-1\end{matrix}\right.\)

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

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

g. \(x\left(2x-3\right)-2\left(3-2x\right)=0\)

\(\Rightarrow x\left(2x-3\right)+2\left(2x-3\right)=0\\ \Rightarrow\left(2x-3\right)\left(x+2\right)=0\\ \Rightarrow\left[{}\begin{matrix}2x-3=0\\x+2=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1.5\\x=-2\end{matrix}\right.\)

Bài 1: 

c) ĐKXĐ: \(x\notin\left\{\dfrac{1}{4};-\dfrac{1}{4}\right\}\)

Ta có: \(\dfrac{3}{1-4x}=\dfrac{2}{4x+1}-\dfrac{8+6x}{16x^2-1}\)

\(\Leftrightarrow\dfrac{-3\left(4x+1\right)}{\left(4x-1\right)\left(4x+1\right)}=\dfrac{2\left(4x-1\right)}{\left(4x+1\right)\left(4x-1\right)}-\dfrac{6x+8}{\left(4x-1\right)\left(4x+1\right)}\)

Suy ra: \(-12x-3=8x-2-6x-8\)

\(\Leftrightarrow-12x-3-2x+10=0\)

\(\Leftrightarrow-14x+7=0\)

\(\Leftrightarrow-14x=-7\)

\(\Leftrightarrow x=\dfrac{1}{2}\)(nhận)

Vậy: \(S=\left\{\dfrac{1}{2}\right\}\)

câu b mình viết nhầm nha 
b,(x+1)^3-(x-2)(x^2+2x+4)

`#3107`

`a)`

`A=`\(3x^4 + \dfrac{1}3xyz - 3x^4 - \dfrac{4}3xyz + 2x^2y - 6z\)

`= (3x^4 - 3x^4) + (1/3xyz - 4/3xyz) + 2x^2y - 6z`

`= -xyz + 2x^2y - 6z`

Thay `x = 1; y = 3` và `z = 1/3` vào A

`A = -1*3*1/3 + 2*1^2*3 - 6*1/3`

`= -1 + 6 - 2`

`= 6 - 3`

`= 3`

Vậy, `A=3`

`b)`

`B=`\(4x^3 - \dfrac{2}7xyz - 4x^3 - \dfrac{4}3xyz + 4x^2y\)

`= (4x^3 - 4x^3) + (-2/7xyz - 4/3xyz) + 4x^2y`

`= -34/21 xyz + 4x^2y`

Thay `x = -1; y = 2` và `z = -1/2` vào B

`B = -34/21*(-1)*2*(-1/2) + 4*(-1)^2 * 2`

`= -34/21 + 8`

`= 134/21`

Vậy, `B = 134/21`

`c)`

`C=`\(4x^2 + \dfrac{1}2xyz - \dfrac{2}3xy^2z - 5x^2yz + \dfrac{3}4xyz\)

`= 4x^2 + (1/2xyz + 3/4xyz) - 2/3xy^2z - 5x^2yz `

`= 4x^2 + 5/4xyz - 2/3xy^2z - 5x^2yz`

Ta có:

`|y| = 2`

`=> y = +-2`

Thay `x = -1; y = 2` và `z = 1/2` vào C

`4*(-1)^2 + 5/4*(-1)*2*1/2 - 2/3*(-1)*2^2*1/2 - 5*(-1)^2*2*1/2`

`= 4 - 5/4 + 4/3 - 5`

`= -11/12`

Vậy, với `x = -1; y = 2; z = 1/2` thì `B = -11/12`

Thay `x = -1; y = -2; z = 1/2`

`B = 4*(-1)^2 + 5/4*(-1)*(-2)*1/2 - 2/3*(-1)*(-2)^2*1/2 - 5*(-1)^2*(-2)*1/2`

`= 4 + 5/4 + 4/3 + 5`

`= 139/12`

Vậy, với `x = -1; y = -2; z = 1/2` thì `B = 139/12.`

1.

a.\(\Leftrightarrow7x-5x=3+12\)

\(\Leftrightarrow2x=15\Leftrightarrow x=\dfrac{15}{2}\)

b.\(\Leftrightarrow6x-10-7x-7=2\)

\(\Leftrightarrow x=-19\)

c.\(\Leftrightarrow1-3x=4x-3\)

\(\Leftrightarrow7x=2\Leftrightarrow x=\dfrac{2}{7}\)

d.\(\Leftrightarrow8x^2-4x+12x-6-8x^2-8x-2=12\)

\(\Leftrightarrow-2=12\left(voli\right)\)

a: \(=4a^3b^3c\left(10xc+3bc-5ab^2x\right)\)

b: \(=\left(b-2c\right)\left(a-b\right)+\left(a+b\right)\left(b-2c\right)\)

=(b-2c)(2a)