Lời giải:

b/

\(\frac{3x+5}{2x^2-5x+3}\geq 0\Leftrightarrow \left[\begin{matrix} \left\{\begin{matrix} 3x+5\geq 0\\ 2x^2-5x+3>0\end{matrix}\right.\\ \left\{\begin{matrix} 3x+5\leq 0\\ 2x^2-5x+3<0\end{matrix}\right.\end{matrix}\right.\)

\(\Leftrightarrow \left[\begin{matrix} \left\{\begin{matrix} x\geq \frac{-5}{3}\\ x>\frac{3}{2}(\text{hoặc}) x< 1\end{matrix}\right.\\ \left\{\begin{matrix} x\leq \frac{-5}{3}\\ 1< x< \frac{3}{2}\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow \left[\begin{matrix} x>\frac{3}{2}\\ \frac{-5}{3}\leq x< 1\end{matrix}\right.\ \)

c/

$2x^3+x+3>0$

$\Leftrightarrow 2x^2(x+1)-2x(x+1)+3(x+1)>0$

$\Leftrightarrow (x+1)(2x^2-2x+3)>0$

$\Leftrightarrow (x+1)[x^2+(x-1)^2+2]>0$

$\Leftrightarrow x+1>0$

$\Leftrightarrow x>-1$

`2x^3 +6x^2 =x^2 +3x`

`<=> 2x^3 +6x^2 -x^2 -3x=0`

`<=> 2x^3 +5x^2 -3x=0`

`<=> x(2x^2 +5x-3)=0`

`<=> x(2x^2 +6x-x-3)=0`

`<=> x[2x(x+3)-(x+3)]=0`

`<=> x(2x-1)(x+3)=0`

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

b)

`(2+x)^2 -(2x-5)^2=0`

`<=> (2+x-2x+5)(2+x+2x-5)=0`

`<=> (-x+7)(3x-3)=0`

\(< =>\left[{}\begin{matrix}-x+7=0\\3x-3=0\end{matrix}\right.\\ < =>\left[{}\begin{matrix}x=7\\x=1\end{matrix}\right.\)

`a) 2x^3 + 6x^2 = x^2 + 3x`

`=> 2x^3 + 6x^2 - x^2 - 3x = 0`

`=> 2x^3 + 5x^2 - 3x = 0`

`=> x(2x^2 + 5x - 3) = 0`

`=> x (2x^2 + 6x - x - 3) = 0`

`=> x [(2x^2 + 6x) - (x+3)] = 0`

`=> x [2x(x+3) - (x+3)] = 0`

`=> x (2x - 1)(x+3) = 0`

`=> x = 0` hoặc `2x - 1 = 0` hoặc `x + 3 = 0`

`=> x = 0` hoặc `x = 1/2` hoặc `x = -3`

`b) (2+x)^2 - (2x-5)^2 = 0`

`=> (2+x+2x-5)(2+x-2x+5) = 0`

`=> (3x - 3)(7-x) = 0`

`=> 3x - 3 = 0` hoặc `7 - x = 0`

`=> x = 1` hoặc `x = 7`

Ta có:

⇔ 6 + 2 + 4x > 2x – 1 – 12

⇔ 4x – 2x > -1 – 12 – 6 – 2

⇔ 2x > -21

⇔ x > -10,5

Vậy tập nghiệm của bất phương trình là {x|x > -10,5}

2 x 3 + 2 x - 1 6 = 4 - x 3

⇔ 2.2x + 2x – 1 = 4.6 – 2x

⇔ 4x + 2x – 1 = 24 – 2x

⇔ 6x + 2x = 24 + 1

⇔ 8x = 25 ⇔ x = 25/8

Phương trình có nghiệm x = 25/8

\(\Leftrightarrow\left(x^2+2x\right)^2+5\left(x^2+2x\right)+6-2=0\)

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

\(\Leftrightarrow\left(x^2+2x+1\right)\left(x^2+2x+4\right)=0\)

=>x+1=0

hay x=-1

\(\left(x^2+2x+2\right)\left(x^2+2x+3\right)-2=0\\ \Leftrightarrow\left(x^2+2x+2\right)\left[\left(x^2+2x+2\right)+1\right]-2=0\\ \Leftrightarrow\left(x^2+2x+2\right)^2+\left(x^2+2x+2\right)-2=0\\ \Leftrightarrow\left[\left(x^2+2x+2\right)^2+2\left(x^2+2x+2\right)\right]-\left[\left(x^2+2x+2\right)+2\right]=0\\ \Leftrightarrow\left(x^2+2x+2\right)\left(x^2+2x+2+2\right)-\left(x^2+2x+2+2\right)=0\\ \Leftrightarrow\left(x^2+2x+2-1\right)\left(x^2+2x+4\right)=0\\ \Leftrightarrow\left(x^2+2x+1\right)\left(x^2+2x+4\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x^2+2x+1=0\\x^2+2x+4=0\end{matrix}\right.\)

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

Đặt \(x^2+2x+2=t\)đk t > 0 

\(t\left(t+1\right)-2=0\Leftrightarrow t^2+t-2=0\Leftrightarrow t=1;t=2\left(ktm\right)\)

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

2:

a: =>2x^2-4x-2=x^2-x-2

=>x^2-3x=0

=>x=0(loại) hoặc x=3

b: =>(x+1)(x+4)<0

=>-4<x<-1

d: =>x^2-2x-7=-x^2+6x-4

=>2x^2-8x-3=0

=>\(x=\dfrac{4\pm\sqrt{22}}{2}\)

\(a,\dfrac{x-3}{x}=\dfrac{x-3}{x+3}\)\(\left(đk:x\ne0,-3\right)\)

\(\Leftrightarrow\dfrac{x-3}{x}-\dfrac{x-3}{x+3}=0\)

\(\Leftrightarrow\dfrac{\left(x-3\right)\left(x+3\right)-x\left(x-3\right)}{x\left(x+3\right)}=0\)

\(\Leftrightarrow x^2-9-x^2+3x=0\)

\(\Leftrightarrow3x-9=0\)

\(\Leftrightarrow3x=9\)

\(\Leftrightarrow x=3\left(n\right)\)

Vậy \(S=\left\{3\right\}\)

\(b,\dfrac{4x-3}{4}>\dfrac{3x-5}{3}-\dfrac{2x-7}{12}\)

\(\Leftrightarrow\dfrac{4x-3}{4}-\dfrac{3x-5}{3}+\dfrac{2x-7}{12}>0\)

\(\Leftrightarrow\dfrac{3\left(4x-3\right)-4\left(3x-5\right)+2x-7}{12}>0\)

\(\Leftrightarrow12x-9-12x+20+2x-7>0\)

\(\Leftrightarrow2x+4>0\)

\(\Leftrightarrow2x>-4\)

\(\Leftrightarrow x>-2\)