Rút gọn biểu thức: (x-2)^2 + x(x^2+x+1)-x(x-2)(x+2) (2x +3)^2+(2x-3)^2 -2(2x+3)(2x-3) x(x+4)(x-4) -(x^2 + 1)(x^2 – 1) (y-3)(y+3)(y^2+9) – (y^2 +2 )(y

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1. `(x-2)^2 +x(+x^2 +x+1)-x(x-2)(x+2)`

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

   `=x^2 -4x+4+x^3 +x^2 +x-x^3 +4x`

   `=2x^2 +x+4`

   `(2x+3)^2 +(2x-3)^2 -2(2x+3)(2x-3)`

   `=4x^2 +12x +9 +4x^2 -12x+9 -2(4x^2 -9)`

   `=8x^2 +18-8x^2 +18`

   `=36`

   `x(x+4)(x-4)-(x^2 +1)(x^2 -1)`

   `=x(x^2 -16)-(x^4 -1)`

   `=x^3 -16x -x^4 +1`

   `=-x^4 +x^3 -16x+1`

   `(y-3)(y+3)(y^2 +9)-(y^2 +2)(y^2 -2)`

   `=(y^2 -9)(y^2 +9)-(y^4 -4)`

   `=y^4 -81 -y^4 +4`

   `=-77`

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