Đáp án+Giải thích các bước giải:
a,
`x^2-10x+16=0`
`⇔x^2-8x-2x+16=0`
`⇔x(x-8)-2(x-8)=0`
`⇔(x-2)(x-8)=0`
$⇔\left[\begin{array}x-2=0\\x-8=0\end{array}\right.$
$⇔\left[\begin{array}x=2\\x=8\end{array}\right.$
Vậy `S={2;8}`
b,
`x^2-11x-26=0`
`⇔x^2-13x+2x-26=0`
`⇔x(x-13)+2(x-13)=0`
`⇔(x+2)(x-13)=0`
$⇔\left[\begin{array}x+2=0\\x-13=0\end{array}\right.$
$⇔\left[\begin{array}x=-2\\x=13\end{array}\right.$
Vậy `S={-2;13}`
c,
`2x^2+7x-4=0`
`⇔2x^2+8x-x-4=0`
`⇔2x(x+4)-(x+4)=0`
`⇔(2x-1)(x+4)=0`
$⇔\left[\begin{array}2x-1=0\\x+4=0\end{array}\right.$
$⇔\left[\begin{array}2x=1\\x=-4\end{array}\right.$
$⇔\left[\begin{array}x=\dfrac{1}{2}\\x=-4\end{array}\right.$
Vậy `S={\frac{1}{2};-4}`
