Đáp án+Giải thích các bước giải:

$c)$ $xy(x+y)-yz(y+z)-zx(z-x)$

=$y[x(x+y)-z(y+z)]$-$zx(z-x)$

=$y(x-z)(x+y+z)$-$zx(z-x)$

=$y(x-z)(x+y+z)$+$zx(x-z)$

=$(x-z)[(y(x+y+z)+zx)$

=$(x-z)$$(xy+$$y^{2}$ +$yz+zx$)

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

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