Tính a) (2x-y+2)^2 b)(xy/2-x/3).(xy/2+x/3) ko lm tắt nha

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1. a,

   $(2x-y+2)^2$

   $= (2x-y+2)(2x-y+2)$

   $= 4x^2-2xy+4x-2xy+y^2-2y+4x-2y+4$

   $= 4x^2+y^2-4xy+8x-4y+4$

   b,

   $(\dfrac{xy}{2}-\dfrac{x}{3})(\dfrac{xy}{2}+\dfrac{x}{3})$

   $=(\dfrac{xy}{2})^2-(\dfrac{x}{3})^2$

   $=\dfrac{x^2y^2}{4}-\dfrac{x^2}{9}$

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2. a) $(2x-y+2)^2$

   $=(2x-y+2).(2x-y+2)$

   $=[(2x-y+2).2x]-[(2x-y+2).y]+[(2x-y+2).2]$

   $=[4x^2-2xy+4x]-[2xy-y^2+2y]+[4x-2y+4]$

   $=4x^2-2xy+4x-2xy+y^2-2y+4x-2y+4$

   $=4x^2+y^2+(-2xy-2xy)+(4x+4x)+(-2y-2y)+4$

   $=4x^2+y^2-4xy+8x-4y+4$

   b) $(\dfrac{xy}{2}-\dfrac{x}{3})(\dfrac{xy}{2}+\dfrac{x}{3})$

   $=[(\dfrac{xy}{2}-\dfrac{x}{3}).\dfrac{xy}{2}]+[(\dfrac{xy}{2}-\dfrac{x}{3}).\dfrac{x}{3}]$

   $=[\dfrac{x^2y^2}{4}-\dfrac{x^2y}{6}]+[\dfrac{x^2y}{6}-\dfrac{x^2}{9}]$

   $=\dfrac{x^2y^2}{4}-\dfrac{x^2y}{6}+\dfrac{x^2y}{6}-\dfrac{x^2}{9}$

   $=\dfrac{x^2y^2}{4}+(-\dfrac{x^2}{y}+\dfrac{x^2y}{6})-\dfrac{x^2}{9}$

   $=\dfrac{x^2y^2}{4}-\dfrac{x^2}{9}$

    

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