`1)5x²+36x+7=0`
`⇔5x²+35x+x+7=0`
`⇔5x(x+7)+(x+7)=0`
`⇔(x+7)(5x+1)=0`
`⇔`$\left[\begin{matrix} x+7=0\\ 5x+1=0\end{matrix}\right.$
`⇔`$\left[\begin{matrix} x=-7\\ x=-\dfrac{1}{5}\end{matrix}\right.$
Vậy `S={-7;-1/5}`
`2)2x²-2x-4=0`
`⇔2x²+2x-4x-4=0`
`⇔2x(x+1)-4(x+1)=0`
`⇔(x+1)(2x-4)=0`
`⇔`$\left[\begin{matrix} x+1=0\\ 2x-4=0\end{matrix}\right.$
`⇔`$\left[\begin{matrix} x=-1\\ x=2\end{matrix}\right.$
Vậy `S={-1;2}`
`3)x²-9x+8=0`
`⇔x²-8x-x+8=0`
`⇔x(x-8)-(x-8)=0`
`⇔(x-8)(x-1)=0`
`⇔`$\left[\begin{matrix} x-8=0\\ x-1=0\end{matrix}\right.$
`⇔`$\left[\begin{matrix} x=8\\ x=1\end{matrix}\right.$
Vậy `S={8;1}`
`4)x²-7x+6=0`
`⇔x²-6x-x+6=0`
`⇔x(x-6)-(x-6)=0`
`⇔(x-6)(x-1)=0`
`⇔`$\left[\begin{matrix} x-6=0\\ x-1=0\end{matrix}\right.$
`⇔`$\left[\begin{matrix} x=6\\ x=1\end{matrix}\right.$
Vậy `S={6;1}`
`5)x²+10x-11=0`
`⇔x²+11x-x-11=0`
`⇔x(x+11)-(x+11)=0`
`⇔(x+11)(x-1)=0`
`⇔`$\left[\begin{matrix} x+11=0\\ x-1=0\end{matrix}\right.$
`⇔`$\left[\begin{matrix} x=-11\\ x=1\end{matrix}\right.$
Vậy `S={-11;1}`
`6)3x²-8x+5=0`
`⇔3x²-3x-5x+5=0`
`⇔3x(x-1)-5(x-1)=0`
`⇔(x-1)(3x-5)=0`
`⇔`$\left[\begin{matrix} x-1=0\\ 3x-5=0\end{matrix}\right.$
`⇔`$\left[\begin{matrix} x=1\\ x=\dfrac{5}{3}\end{matrix}\right.$
Vậy `S={1;5/3}`
`7)-2x²+3x-1=0`
`⇔-2x²+2x+x-1=0`
`⇔-2x(x-1)+(x-1)=0`
`⇔(x-1)(-2x+1)=0`
`⇔`$\left[\begin{matrix} x-1=0\\ -2x+1=0\end{matrix}\right.$
`⇔`$\left[\begin{matrix} x=1\\ x=\dfrac{1}{2}\end{matrix}\right.$
Vậy `S={1;1/2}`
`8)5x²-7x+2=0`
`⇔5x²-5x-2x+2=0`
`⇔5x(x-1)-2(x-1)=0`
`⇔(x-1)(5x-2)=0`
`⇔`$\left[\begin{matrix} x-1=0\\ 5x-2=0\end{matrix}\right.$
`⇔`$\left[\begin{matrix} x=1\\ x=\dfrac{2}{5}\end{matrix}\right.$
Vậy `S={1;2/5}`
`9)-x²+4x+5=0`
`⇔-x²-x+5x+5=0`
`⇔-x(x+1)+5(x+1)=0`
`⇔(x+1)(-x+5)=0`
`⇔`$\left[\begin{matrix} x+1=0\\ -x+5=0\end{matrix}\right.$
`⇔`$\left[\begin{matrix} x=-1\\ x=5\end{matrix}\right.$
Vậy `S={-1;5}`
`10)x²-8x+16=0`
`⇔x²-2.x.4+4²=0`
`⇔(x-4)²=0`
`⇔x-4=0`
`⇔x=4`
Vậy `S={4}`
