`#Sad`
`5)`
`(2x-1)(2x+1)-(2x-2)^2-2x = 0`
`⇔ 4x^2-1-4x^2+8x-4-2x = 0`
`⇔ (4x^2-4x^2)+(8x-2x)+(-1-4) = 0`
`⇔ 6x-5 = 0`
`⇔ 6x = 5`
`⇔ x = 5/6`
`\text{Vậy}` `x=5/6`
`\text{→Áp dụng:}`
`+)` `(A-B)^2 = A^2-2AB+B^2`
`+)` `A^2-B^2 = (A-B)(A+B)`
`6)`
`3(x-1)^2-3x(x-5) = 1`
`⇔ 3(x^2-2x+1)-(3x^2-15x)-1=0`
`⇔ 3x^2-6x+3-3x^2+15x-1 = 0`
`⇔ (3x^2-3x^2)+(-6x+15x)+(3-1) = 0`
`⇔ 9x+2 = 0`
`⇔ 9x = -2`
`⇔ x = -2/9`
`\text{Vậy}` `x=-2/9`
`\text{→Áp dụng:}` `(A-B)^2 = A^2-2AB+B^2`
