`#Sad`
`\text{·Bài 1:}`
`e,`
`x^2+4x+4-y^2`
`= (x^2+4x+4)-y^2`
`= (x+2)^2-y^2`
`= (x-y+2)(x+y+2)`
`g,`
`x^2-16-4xy+4y^2`
`= (x^2-4xy+4y^2)-16`
`= (x-2y)^2-16`
`= (x-2y-4)(x-2y+4)`
`l,`
`x^2-7x+6`
`= x^2-6x-x+6`
`= (x^2-6x)-(x-6)`
`= x(x-6)-(x-6)`
`= (x-1)(x-6)`
`m,`
`x^2-x-56`
`= x^2-8x+7x-56`
`= (x^2-8x)+(7x-56)`
`= x(x-8)+7(x-8)`
`= (x+7)(x-8)`
`n,`
`5x^2-x-4`
`= 5x^2-5x+4x-4`
`= (5x^2-5x)+(4x-4)`
`= 5x(x-1)+4(x-1)`
`= (5x+4)(x-1)`
`\text{·Bài 2:}`
`c,`
`(2x-1)^2 = (x+3)^2`
`⇔ 4x^2-4x+1 = x^2+6x+9`
`⇔ 4x^2-x^2-4x-6x = -1+9`
`⇔ 3x^2-10x-8 = 0`
`⇔ (x-4)(3x+2) = 0`
`⇔`\(\left[ \begin{array}{l}x-4=0\\3x+2=0\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=4\\3x=-2\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=4\\x=\dfrac{-2}{3}\end{array} \right.\)
`\text{Vậy S=}` `{ 4 ; -2/3 }`
`d,`
`x^2(x-2)-2x^2+8x-8 = 0`
`⇔ x^3-2x^2-2x^2+8x-8 = 0`
`⇔ x^3-4x^2+8x-8 = 0`
`⇔ (x^3-8)-(4x^2-8x) = 0`
`⇔ (x-2)(x^2+2x+4)-4x(x-2) = 0`
`⇔ (x-2)(x^2+2x+4-4x) = 0`
`⇔ (x-2)(x^2-2x+4) = 0`
`\text{·Ta có:}` `x^2-2x+4 = (x-1)^2+3`
`\text{Mà}` `(x-1)^2 >= 0`
`⇒(x-1)^2+3>0` `\text{(Không thỏa mãn)}`
`⇔ x-2 = 0`
`⇔ x = 2`
`\text{Vậy S=}` `{ 2 }`
