Thực hiện phép tính ​2. (x2 – 2xy +y2 )(x-2y) 3. (x+y+z)(x-y+z)​4, 12a2b(a-b)(a+b) 5, (2×2-3x+5)(x2-8x+2)

2. (x2 – 2xy +y2 )(x-2y)

= (2x – 2xy +2y)( x-2y)

=  2x² – 2x²y +2xy -2xy + 2xy² + 4y²

= 2x² – 2x²y +2xy² + 4y² + (2xy -2xy)

= 2x² – 2x²y +2xy² + 4y²

3.  (x+y+z)(x-y+z)​

= x² -xy + xz + xy – y² + yz + xz +yz +z²

= x² -y² + z² + (xy-xy) + (xz+xz) + (yz + yz)

= x² – y² + z² + 2xz + 2yz

4. 12a2b(a-b)(a+b)

= 24ab(a-b)(a+b)

= (24a²b – 24ab²)(a+b)

= 24a³b + 24a²b² – 24a²b² – 24ab³

= 24a³b – 24ab³

 5. (2×2-3x+5)(x2-8x+2)

= (4x – 3x +5)( 2x -8x +2)

= 8x² – 32x² + 8x – 6x² + 24x² -6x +10x -40x +10

= (8x² -32x² – 6x² +24x²) + ( 8x – 6x +10x -40x ) +10

= -6x²  28x +10

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