tách nha m.n : a)x^2 +7x+12 b)6x^2+13x+6 C)3x^2-10x+7 d)5x^2-14x-3 e)4x^2-5x-6 f)15x^2+7x-2 g)12x^2 +7x-12 h)x^2-5x-14 2x^2+5x+2

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1. Đáp án:

    

   Giải thích các bước giải:

   a)`x^2 +7x+12`

   `=(x^2+3x)+(4x+12)`

   `=x(x+3)+4(x+3)`

   `=(x+3)(x+4)`

   b)`6x^2+13x+6`

   `=6x^2+4x+9x+6`

   `=2x(3x+2)+3(3x+2)`

   `=(2x+3)(3x+2)`

   c)`3×2−10x+7`

   `=3×2−3x−7x+7`

   `=3x(x−1)−7(x−1)`

   `=(3x−7)(x−1)`

   d)`5x^2-14x-3`

   `= 5x^2 – 15x + x – 3`

   `= 5x( x-3 ) + ( x-3 )`

   `= ( x – 3)( 5x+1 )`

   e)`4x^2-5x-6`

   `=4×2-8x+3x-6`

   `=4x(x-2)+3(x-2)`

   `=(x-2)(4x+3)`

   f)`15x^2+7x-2`

   `=15x^2+10x−3x−2`

   `=(15x^2+10x)−(3x+2)`

   `=5x(3x+2)−1(3x−2)`

   `=(5x−1)(3x+2)`

   g)`12x^2 +7x-12`

   `=12x^2-9x+16x-12`

   `=3x(4x-3)+4(4x-3)`

   `=(4x-3)(3x+4)`

   h)`x^2-5x-14`

   `=x^2−7x+2x−14`

   `=x(x−7)+2(x−7)` `

   `=(x−7)(x+2)`

   i) `2x^2+5x+2`

   `=2x^2+4x+x+2`

   `= 2x(x+2)+(x+2)`

   `= (2x+1)(x+2)`

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