Đáp án:
`↓↓`
Giải thích các bước giải:
`1)`
`a) 2x(x – 3) + 5(x – 3)`
`= (x-3)(2x+5)`
`b) (x^2 – 4) + (x – 2)(3 – 2x)`
`= (x-2)(x+2) - (x-2)(3-2x)`
`= (x-2)( x + 2 - 3 + 2x )`
`= ( x - 2 )( 3x - 1 )`
`d) x(2x – 7) – 4x + 14`
`= x(2x-7) - 2( 2x - 7 )`
`= ( 2x - 7 )( x - 2) `
`e) x( 2x – 9) – 3x(x – 5)`
`= 2x^2 - 9x - 3x^2 + 15x `
`= -x^2 + 6x `
`= x( 6 - x ) `
`f) 3x – 15 – 2x(x – 5)`
`= 3x -15 - 2x^2 + 10x `
`= -2x^2 + 13x - 15 `
` = -2x^2 + 10x + 3x - 15 `
`= -2x ( x - 5 ) + 3(x - 5 ) `
`= (x-5)(3-2x) `
`g) (x^2 – 2x + 1) – 4`
`= (x-1)^2 - 4 `
`= ( x- 1 - 4 )(x - 1 + 4 ) `
`= ( x - 5 )( x + 3 ) `
`h) x^2 – 5x + 6`
`= x^2 - 2x - 3x + 6 `
`= x(x-2) - 3(x-2) `
`= (x-2)(x-3) `
`n) x^2 – 9 + (x – 3)^2`
`= ( x - 3 )(x + 3 ) + ( x - 3 )^2`
`= (x-3)( x + 3 + x - 3 ) `
`= 2x( x - 3 )`
`m) x^3 – 4x^2 – 12x + 27`
`= x^3+ 3x^2 - 7x^2 - 21x + 9x + 27`
`= x^2( x +3 ) - 7x ( x + 3 ) + 9( x + 3 ) `
`= ( x + 3 )( x^2 - 7x + 9 ) `
`2)`
`a) 5x + 1 = 3 + 4x`
`<=> x = 2 `
`b) 4x - 2 + 3x = - 5x + 2`
`<=> 12x = 4 `
`<=> x = 1/3 . `
