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y(x+y)+yz(y+z)+xz(x+z)+2xyz
= xy(x + y) + yz(y + z) + xyz + xz(x + z) + xyz
= xy(x + y) + yz(y + z + x) + xz(x + z + y)
= xy(x + y) + z(x + y + z)(y + x)
= (x + y)(xy + zx + zy + z²)
= (x + y)[x(y + z) + z(y + z)]
= (x + y)(y + z)(z + x)
Ta có :
\(\left(x+y\right)\left(x^2-y^2\right)+\left(y+z\right)\left(y^2-z^2\right)+\left(z+x\right)\left(z^2-x^2\right)\)
\(=\left(x+y\right)^2.\left(x-y\right)+\left(y+z\right).\left(y^2-x^2+x^2-z^2\right)+\left(z+x\right)\left(z^2-x^2\right)\)
\(=\left(x+y\right)\left(x^2-y^2\right)-\left(y+z\right)\left(x^2-y^2+z^2-x^2\right)+\left(z+x\right)\left(z^2-x^2\right)\)
\(=\left(x+y\right)\left(x^2-y^2\right)-\left(y+z\right)\left(x^2-y^2\right)-\left(y+z\right)\left(z^2-x^2\right)+\left(z+x\right)\left(z^2-x^2\right)\)
\(=\left(x^2-y^2\right)\left(x+y-y-z\right)-\left(z^2-x^2\right).\left(y+z-z-x\right)\)
\(=\left(x^2-y^2\right).\left(x-z\right)-\left(z^2-x^2\right).\left(y-x\right)\)
\(=\left(x-y\right)\left(x+y\right)\left(x-z\right)+\left(z-x\right)\left(z+x\right)\left(x-y\right)\)
\(=\left(x-y\right).\left[\left(x+y\right)\left(x-z\right)+\left(z-x\right).\left(x+z\right)\right]\)
\(=\left(x-y\right)\left(x^2-zx+xy-yz+zx+z^2-x^2-xz\right)\)
\(=\left(x-y\right)\left(z^2-zx+xy-yz\right)\)
\(=\left(x-y\right)\left[z.\left(z-x\right)-y.\left(z-x\right)\right]\)
\(=\left(x-y\right)\left(z-y\right)\left(z-x\right)\)
\(=\left(x-y\right)\left(y-z\right)\left(x-z\right)\)
Ta có :
\(\left(x+y\right)\left(x^2-y^2\right)+\left(y+z\right)\left(y^2-z^2\right)+\left(z+x\right)\left(z^2-x^2\right)\)
\(=\left(x+y\right)^2.\left(x-y\right)+\left(y+z\right).\left(y^2-x^2+x^2-z^2\right)+\left(z+x\right)\left(z^2-x^2\right)\)
\(=\left(x+y\right)\left(x^2-y^2\right)-\left(y+z\right)\left(x^2-y^2+z^2-x^2\right)+\left(z+x\right)\left(z^2-x^2\right)\)
\(=\left(x+y\right)\left(x^2-y^2\right)-\left(y+z\right)\left(x^2-y^2\right)-\left(y+z\right)\left(z^2-x^2\right)+\left(z+x\right)\left(z^2-x^2\right)\)
\(=\left(x^2-y^2\right)\left(x+y-y-z\right)-\left(z^2-x^2\right).\left(y+z-z-x\right)\)
\(=\left(x^2-y^2\right).\left(x-z\right)-\left(z^2-x^2\right).\left(y-x\right)\)
\(=\left(x-y\right)\left(x+y\right)\left(x-z\right)+\left(z-x\right)\left(z+x\right)\left(x-y\right)\)
\(=\left(x-y\right).\left[\left(x+y\right)\left(x-z\right)+\left(z-x\right).\left(x+z\right)\right]\)
\(=\left(x-y\right)\left(x^2-zx+xy-yz+zx+z^2-x^2-xz\right)\)
\(=\left(x-y\right)\left(z^2-zx+xy-yz\right)\)
\(=\left(x-y\right)\left[z.\left(z-x\right)-y.\left(z-x\right)\right]\)
\(=\left(x-y\right)\left(z-y\right)\left(z-x\right)\)
\(=\left(x-y\right)\left(y-z\right)\left(x-z\right)\)
\(\left(x+y\right)\left(x^2-y^2\right)+\left(y+z\right)\left(y^2-z^2\right)+\left(z+x\right)\left(z^2-x^2\right)\)
\(=-xy^2+yx^2-yz^2+zy^2-xz^2+zx^2\)
\(=xy^2\left(1-1\right)+yz^2\left(1-1\right)+zx^2\left(1-1\right)\)
\(=\left(xy^2+yz^2+zx^2\right).0\left(=0\right)\)
nhấn vào đây nhé có 2 cách làm: Chuyên đề Bồi dưỡng học sinh giỏi - Phân tích đa thức thành nhân tử - Giáo Án, Bài Giảng
t i c k mk!! 536546456545576768978045362546115346456575676868784675462552
Câu hỏi của Kim Lê Khánh Vy - Toán lớp 8 - Học toán với OnlineMath
Phân tích các đa thức sau thành nhân tử:
a) x(y2-z2)+y(z2-x2)+z(x2-y2)
b) x(y+z)2+y(z+x)2+z(x+y)2-4xyz
b)x(y+z)2+y(z+x)2+z(x+y)2-4xyz
=[x(y+z)2-2xyz]+[y(z+x)2-2xyz]+z(x+y)2
=x(y2+2yz+z2-2yz)+y(x2+z2+2xz-2xz)+z(x+y)2
=x(y2+z2)+y(x2+z2)+z(x+y)2
=xy2+xz2+x2y+yz2+(xz+yz)(x+y)
=xy(x+y)+z2(x+y)+(xz+yz)(x+y)
=(x+y)(xy+z2+xz+yz)
=(x+y)[x(y+z)+z(y+z)]
=(x+y)(y+z)(x+z)
a)x(y2-z2)+y(z2-x2)+z(x2-y2)
=x(y-z)(y+z)+yz2-x2y+x2z-y2z
=(y-z)(xy+xz)-x2(y-z)-yz(y-z)
=(y-z)(xy+xz-x2-yz)
=(y-z)[x(y-x)-z(y-x)]
=(y-z)(y-x)(x-z)
\(=x^2y-x^2z+y^2z-y^2x+z^2\left(x-y\right)\)
\(=x^2y-y^2x-x^2z+y^2z+z^2\left(x-y\right)\)
\(=xy\left(x-y\right)-z\left(x^2-y^2\right)+z^2\left(x-y\right)\)
\(=\left(x-y\right)\left(xy-z\left(x+y\right)+z^2\right)\)
\(=\left(x-y\right)\left(xy-zx+z^2-zy\right)=\left(x-y\right)\left[x\left(y-z\right)-z\left(y-z\right)\right]\)
\(=\left(x-y\right)\left(y-z\right)\left(x-z\right)\)
= x2 (y-z) +y2(z-x) +z2 (-(y-z)-(z-x))
= x2 (y-z) +y2 (z-x) - z2(y-z) -z2(z-x)
= (y-z) (x2 -z2) +(z-x) (y2 - z2)
= (y-z) (x-z) (x+z) + (z-x) (y-z) (y+z)
=(y-z) (x-z) (x+z) - (x-z) (y-z) (y+z)
=(y-z) (x-z) (x+z-y-z)
=(y-z) (x-z) (x-y)