Tìm x a. 5x ( x – 3 ) – 2x + 6 = 0 b. ( x + 2 )^2 – ( x – 2 ) ( x + 2 ) = 0 c. x^3 – 8 = ( x – 2 )^2 d. x^3 + 5x^2 – 4x – 20 = 0 HELP ME……..

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1. `a) 5x(x – 3) – 2x + 6 = 0`
   `⇒ 5x(x – 3) – 2(x-3) = 0`
   `⇒ (x-3)(5x-2)=0`
   `⇒ x=3` hoặc `x= 2/5`

   `b) (x+2)^2-(x-2)(x+2)=0`

   `=> x^2+4x+4-(x^2-2^2)=0`

   `=> x^2+4x+4-x^2+4=0`

   `=> 4x+8=0`

   `=> 4x=-8`

   `=> x=-2`

   `c) x^3-8=(x-2)^3`

   `=> x^3-8-(x-2)^3=0`

   `=>x^3-8-x^3+6x^2-12x+8=0`

   `=> 6x^2-12x=0`

   `=> 6x(x-2)=0`

   `=> 6x=0` hoặc `x-2=0`

   `=> x=0` hoặc `x=2`

   `d) `

   `x^3 – 5x^2 – 4x + 20 =0`
   `=> x^2(x-5)-4(x-5)=0`
   `=> (x^2-4)(x-5)=0`
   `=> (x+2)(x-2)(x-5)=0`
   `=> x+2 = 0` hoặc `x-2 = 0` hoặc `x-5 =0`
   `=> x = -2` hoặc `x = 2` hoặc `x = 5`

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