`a)x( x-2 ) + x - 2 = 0 `
`<=>x(x-2)+(x-2)=0`
`<=>(x+1)(x-2)=0`
`<=>`\(\left[ \begin{array}{l}x+1=0\\x-2=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=-1\\x=2\end{array} \right.\)
Vậy `S={-1;2}`
`b) 5x( x-3 ) - x+3 = 0 `
`<=>5x( x-3 ) - (x-3)=0`
`<=>(x-3)(5x-1)=0`
`<=>`\(\left[ \begin{array}{l}x-3=0\\5x-1=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=3\\5x=1\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=3\\x=1/5\end{array} \right.\)
Vậy `S={3;1/5}`
`c)(3x + 5)(4 - 3x) = 0`
`<=>`\(\left[ \begin{array}{l}3x+5=0\\4-3x=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}3x=-5\\-3x=-4\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=-5/3\\x=3/4\end{array} \right.\)
Vậy `S={-5/3;3/4}`
`d)3x(x - 7) -2(x - 7) = 0`
`<=>(x-7)(3x-2)=0`
`<=>`\(\left[ \begin{array}{l}x-7=0\\3x-2=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=7\\3x=2\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=7\\x=2/3\end{array} \right.\)
Vậy `S={7;2/3}`
`e)7x^2 - 28 = 0`
`<=>7(x^2-4)=0`
`<=>7(x^2-2^2)=0`
`<=>7(x-2)(x+2)=0`
`<=>(x-2)(x+2)=0`
`<=>`\(\left[ \begin{array}{l}x-2=0\\x+2=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=2\\x=-2\end{array} \right.\)
Vậy `S={-2;+2}`
`f)(2x + 1) + x(2x + 1) = 0`
`<=>(2x+1)(x+1)=0`
`<=>`\(\left[ \begin{array}{l}2x+1=0\\x+1=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}2x=-1\\x=-1\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=-1/2\\x=-1\end{array} \right.\)
Vậy `S={-1/2;-1}`
`g)2x^3 - 50x = 0`
`<=>2x(x^2-25)=0`
`<=>2x(x-5)(x+5)=0`
`<=>2x=0` hoặc `x-5=0` hoặc `x+5=0`
`<=>x=0` hoặc `x=5` hoặc `x=-5`
Vậy `S={0;5;-5}`
`h)2x(3x-5)-(5-3x)=0`
`<=>2x(3x-5)+(3x-5)=0`
`<=>(3x-5)(2x+1)=0`
`<=>`\(\left[ \begin{array}{l}3x-5=0\\2x+2=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}3x=5\\2x=-2\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=3/5\\x=-1\end{array} \right.\)
Vậy `S={3/5;-1}`
