[Toán 6] Rút gọn biểu thức

B

braga

[TEX]a) \ x(y-z ) +y(z-x )+ z (x+y) \\ =xy-xz+yz-xy+zx+zy \\ = 2yz \\\\ b) \ (x -y+z )- (x -y-z) +(x+y-z ) -(x+y+z) \\ =x-y+z-x+y+z+x+y+z-x-y-z \\ =2z[/TEX]
 
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