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a)xy(x-y)-xz(y-z)-xz(x-y)+yz(y-z)

b)(a-x)(x-y)(y+x+a)-(y-x)(x-a)(y-x-a)

а)    (х-у)(ху-хz)+(у-z)(xz-yz)

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

b)(a-x)(x-y)(y+x+a)-(y-x)(x-a)(y-x-a)=(a-x)(x-y)(y+x+a)+(x-y)(x-a)(y-x-a)=(a-x)(x-y)(y+x+a)-(x-y)(a-x)(y-x-a)=(a-x)(x-y)(y+x+a-(y-x-a))=(a-x)(x-y)(2x+2a)=2(a-x)(x-y)(a+x)=2(x-y)(a^(2)-x^(2))