a)
`(x+1)(2x-3)=(2x-1)(x+5)`
`↔2x^2-x-3=2x^2+9x-5`
`↔-10x=-2`
`↔x=1/5`
Vậy `S={1/5}`
b)
`2x(x+2)^2-8x^2=2(x-2)(x^2+2x+4)`
`↔2x(x^2+4x+4)-8x^2=2(x^3-8)`
`↔2x^3+8x^2+8x-8x^2-2x^3+16=0`
`↔8x=-16`
`↔x=-3`
Vậy `S={-3}`
c)
`(x+2)^2-(2x+1)^2=3x(1-x)`
`↔(x+2-2x-1)(x+2+2x+1)=3x-3x^2`
`↔(-x+1)(3x+3)=3x-3x^2`
`↔-3x^2+3=3x-3x^2`
`↔-3x=-3`
`↔x=1`
Vậy `S={1}`
d)
`(x+3)(2x-3)+4x^2=9`
`↔(x+3)(2x-3)+4x^2-9=0`
`↔(x+3)(2x-3)+(2x+3)(2x-3)=0`
`↔(2x-3)(x+3+2x+3)=0`
`↔(2x-3)(3x+6)=0`
`↔` \(\left[ \begin{array}{l}2x-3=0\\3x+6=0\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=\dfrac{3}{2}\\x=-2\end{array} \right.\)
Vậy `S={3/2;-2}`
e)
`(x+3)^3=9(x+3)`
`↔(x+3)^3-9(x+3)=0`
`↔(x+3)[(x+3)^2-9]=0`
`↔(x+3)[(x+3)^2-3^2]=0`
`↔(x+3)[(x+3-3)(x+3+3)]=0`
`↔x(x+3)(x+6)=0`
`↔` \(\left[ \begin{array}{l}x=0\\x+3=0\\x+6=0\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=0\\x=-3\\x=-6\end{array} \right.\)
Vậy `S={0;-3;-6}`
