Toán nâng cao 8

M

manhnguyen0164

a. $yz(y+z)+xz(z-x)- xy(x+y)=yz(y+z)+xz[(y+z)-(x+y)]-xy(x+y)$

$=(y+z)(yz+xz)-(x+y)(xz+xy)=z(x+y)(y+z)-x(x+y)(y+z)=(x+y)(y+z)(z-x)$
 
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