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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: bài 1 tính a ) (x/y – y ) *( x/2 + y )

Toán Lớp 7: bài 1 tính
a ) (x/y – y ) *( x/2 + y )

Comments ( 2 )

  1. a. $\left(\dfrac xy-y\right)\left(\dfrac x2 +y\right)$
    $= \dfrac xy \left(\dfrac x2 +y\right) – y\left(\dfrac x2 +y\right)$
    $= \dfrac{x^2}{2y}+\dfrac{xy}{y}-\dfrac{xy}{2}-y^2$
    $= \dfrac{x^2}{2y}+x-\dfrac{xy}{2}-y^2$

  2. (x/y – y)(x/2 +y)
    = (x/y . x/2) + (x/y . y) + (-y . x/2) + (-y . y)
    = x^2/{2y} + x  – {xy}/2 – y^2          
     

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222-9+11+12:2*14+14 = ? ( )