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x(y+z)^2 - y(z-x)^2 +z(x+y)^2 - x^3 + y^3 - z^3 - 4xyz
=xy^2+2xyz+xz^2-yz^2+2xyz-x^2y+x^2z+2xyz+zy^2-x^3+y^3-z^3-4xyz
=xy^2+xz^2-yz^2-x^2y+x^2z+y^2z-x^3+y^3-z^3+2xyz
=(xy^2+2xyz+xz^2)-x^3-(yz^2+2xyz+x^2y)+y^3+(x^2z+2xyz+y^2z)-z^3
=x[(y+z)^2-x^2)-y[(z+x)^2-y^2]+z[(x+y)^2-z^2]
=x(-x+y+z)(x+y+z)-y(x-y+z)(x+y+z)+z(x+y-z)(x+y+z)
=(x+y+z)[-x^2+xy+xz-xy+y^2-yz+xz+yz-z^2]
=(x+y+z)[-x(x-y-z)-y(x-y-z)+z(x-y-z)]
=(x+y+z)(x-y-z)(z-x-y)
tham khảo:https://hoc247.net/hoi-dap/toan-8/phan-tich-da-thuc-x-2-y-2-3-z-2-x-2-3-y-2-z-2-3-thanh-nhan-tu-faq358831.html
Đây bạn nhé
Bạn làm theo người này nhé, mik cũng khum bt. mik chỉ nhắc để bn có đáp án nhanh nhất thui
x(y+z)^2 - y(z-x)^2 +z(x+y)^2 - x^3 + y^3 - z^3 - 4xyz
=xy^2+2xyz+xz^2-yz^2+2xyz-x^2y+x^2z+2xyz+zy^2-x^3+y^3-z^3-4xyz
=xy^2+xz^2-yz^2-x^2y+x^2z+y^2z-x^3+y^3-z^3+2xyz
=(xy^2+2xyz+xz^2)-x^3-(yz^2+2xyz+x^2y)+y^3+(x^2z+2xyz+y^2z)-z^3
=x[(y+z)^2-x^2)-y[(z+x)^2-y^2]+z[(x+y)^2-z^2]
=x(-x+y+z)(x+y+z)-y(x-y+z)(x+y+z)+z(x+y-z)(x+y+z)
=(x+y+z)[-x^2+xy+xz-xy+y^2-yz+xz+yz-z^2]
=(x+y+z)[-x(x-y-z)-y(x-y-z)+z(x-y-z)]
=(x+y+z)(x-y-z)(z-x-y)
\(z^3\left(x+y^2\right)+y^3\left(z-x^2\right)-x^3\left(y+z^2\right)-xyz\left(xyz-1\right)\)
\(=xz^3+y^2z^3+y^3z-x^2y^3-x^3-x^3z^2-x^2y^2z^2+xyz\)
\(=\left(y^2z^3+y^3z\right)+\left(xz^3+xyz\right)-\left(x^2y^3+x^2y^2z^2\right)-x^3\left(y+z^2\right)\)
\(=y^2z\left(y+z^2\right)+xz\left(y+z^2\right)-x^2y^2\left(y+z^2\right)-x^3\left(y+z^2\right)\)
\(=\left(y+z^2\right)\left(y^2z+xz-x^2y^2-x^3\right)\)
\(=\left(y+z^2\right)\left[z\left(y^2+x\right)-x^2\left(y^2+x\right)\right]\)
\(=\left(y+z^2\right)\left(z-x^2\right)\left(y^2+x\right)\)
Tick hộ nha bạn 😘
c1:
x3+3x2+3x+1-27z3
=(x+1)3-(3z)3
=(x+1-3z)[(x+1)2-(x+1)3z+9z2)
=(x+1-3z)(x2+2x+1-3xz-3z+9x2)
c2:
x2-2xy+y2-xz+yz
=(x-y)2-z(x-y)
=(x-y)(x-y-z)
Ta có (x^2 + y^2 )^3 + (z^2 – x^2 )^3 – (y^2 + z^2 )^3
= (x^2 + y^2 )^3 + (z^2 – x^2 )^3 + (-y^2 - z^2 )^3
Ta thấy x^2 + y^2 + z^2 – x^2 – y^2 – z^2 = 0
=> áp dụng nhận xét ta có: (x^2+y^2 )^3+ (z^2 -x^2 )^3 -y^2 -z^2 )^3
=3(x^2 + y^2 ) (z^2 –x^2 ) (-y^2 – z^2 )
= 3(x^2+y^2 ) (x+z)(x-z)(y^2+z^2 )
\((x^2+y^2)^3+(z^2-x^2)^3-(y^2+z^2)^3\)
\(=-3[x^4y^2-x^4z^2-x^2y^2z^2+x^2z^4-x^2y^4+x^2y^2z^2+y^4z^2-y^2z^4\)
\(=-3[x^2(x^2y^2-x^2z^2-z^2y^2+z^4)-y^2(x^2y^2-x^2z^2-z^2y^2+z^4)\)
\(=-3(x^2-y^2)(x^2y^2-x^2z^2-z^2y^2+z^4)\)
\(=-3(x^2-y^2[x^2(y^2-z^2)-z^2(y^2-z^2)]\)
\(=-3(x^2-y^2)(x^2-z^2)(y^2-z^2)\)
\(=-3(x-y)(x+y)(x-z)(x+z)(y+z)(y-z)\)