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\(\left(a+b+c\right)\left(ab+bc+ca\right)-abc\)
\(=\left(a+b+c\right)\left(ab+bc\right)+\left(a+b+c\right)ac-abc\)
\(=\left(ab+b^2+bc\right)\left(a+c\right)+\left(a+c\right)ac+abc-abc\)
\(=\left(a+c\right)\left(ab+b^2+bc+ac\right)\)
\(=\left(a+b\right)\left(b+c\right)\left(c+a\right)\)
Lời giải:
a)
$(a-x)y^3-(a-y)x^3+(x-y)a^3=(a-x)y^3-[(a-x)+(x-y)]x^3+(x-y)a^3$
$=(a-x)(y^3-x^3)+(x-y)(a^3-x^3)$
$=(a-x)(y-x)(y^2+xy+x^2)-(y-x)(a-x)(a^2+ax+x^2)$
$=(a-x)(y-x)(y^2+xy+x^2-a^2-ax-x^2)$
$=(a-x)(y-x)(y^2+xy-ax-a^2)=(a-x)(y-x)(y-a)(y+a+x)$
b)
$bc(b+c)+ca(c+a)+ba(a+b)+2abc$
$=bc(b+c+a)+ca(c+a+b)+ba(a+b)$
$=(bc+ac)(b+c+a)+ba(a+b)=c(b+a)(b+c+a)+ba(a+b)=(a+b)[c(a+b+c)+ab]$
$=(a+b)[c(a+c)+b(a+c)]=(a+b)(b+c)(c+a)$
c)
$x^2y+xy^2+x^2z+xz^2+y^2z+yz^2+2xyz$
$=xy(x+y)+xz(x+z)+yz(y+z)+2xyz$
$=(x+y)(y+z)(x+z)$ (như phần b)
c/\(=\left(x+y\right)\left(y+z\right)\left(z+x\right)\)
PTĐTTNT chỉ cần có kết quả là bạn có thể tự trình bày
\(\left(a+b+c\right)\left(ab+bc+ca\right)-abc\)
\(=\left(a+b+c\right)\left(ab+bc\right)+\left(a+b+c\right)ac-abc\)
\(=\left(ab+b^2+bc\right)\left(a+c\right)+\left(a+c\right)ac+abc-abc\)
\(=\left(a+c\right)\left(ab+b^2+bc+ac\right)\)
\(=\left(a+b\right)\left(b+c\right)\left(c+a\right)\)
\(C=c\left[b\left(a+d\right)\left(b-c\right)+a\left(b+d\right)\left(c-a\right)\right]+ab\left(c+d\right)\left(a-b\right)\)
\(C=c\left[\left(ab+bd\right)\left(b-c\right)+\left(ab+ad\right)\left(c-a\right)\right]+ab\left(c+d\right)\left(a-b\right)\)
\(C=c\left[ab^2-abc+b^2d-bcd+abc-a^2b+acd-a^2d\right]+ab\left(c+d\right)\left(a-b\right)\)
\(C=c\left[\left(ab^2-a^2b\right)+\left(b^2d-a^2d\right)+\left(acd-bcd\right)\right]+ab\left(c+d\right)\left(a-b\right)\)
\(C=c\left[ab\left(b-a\right)+d\left(a+b\right)\left(b-a\right)+cd\left(a-b\right)\right]+ab\left(c+d\right)\left(a-b\right)\)
\(C=c\left(a-b\right)\left(-ab-da-db+cd\right)+ab\left(c+d\right)\left(a-b\right)\)
\(C=\left(a-b\right)\left(-abc-acd-bcd+c^2d+abc+abd\right)\)
\(C=\left(a-b\right)\left(-acd-bcd+abd+c^2d\right)\)
\(C=c\left(a-b\right)\left(c^2+ab-ac-bc\right)\)
\(C=c\left(a-b\right)\left[\left(c^2-ac\right)-\left(bc-ab\right)\right]\)
\(C=c\left(a-b\right)\left[c\left(c-a\right)-b\left(c-a\right)\right]\)
\(C=c\left(a-b\right)\left(c-a\right)\left(c-b\right)\)
a: \(a\left(x-y\right)-b\left(y-x\right)+c\left(x-y\right)\)
\(=a\left(x-y\right)+b\left(x-y\right)+c\left(x-y\right)\)
\(=\left(x-y\right)\left(a+b+c\right)\)
b: \(a^m-a^{m+2}\)
\(=a^m-a^m\cdot a^2\)
\(=a^m\left(1-a^2\right)\)
\(=a^m\left(1-a\right)\left(1+a\right)\)
a/ x3 + x2 z + y2 z - xyz + y3
= (x + y)(x2 - xy + y2) + z(x2 - xy + y2)
= (x2 - xy + y2)(x + y + z)
Nhiều vậy. Xíu m làm