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27 tháng 6 2016

batngo

10 tháng 11 2021

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)

10 tháng 11 2021

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)

13 tháng 8 2020

Ta có: ( x - y) z3 + ( y - z ) x3 + ( z - x ) y 

= ( x - y ) z3 + ( y - z )x3 + ( z - y)y3 + ( y - x ) y3

= ( x - y ) ( z3 - y) + ( y - z ) ( x3 - y3

= ( x - y ) ( z - y ) ( z2 + zy + y2 ) + ( y - z ) ( x - y) ( x2 + xy + y2 ) 

= ( x - y ) ( y - z ) ( x2 + xy + y2 - z2 - zy - y2

= ( x - y ) ( y - z ) [ ( x2 - z2) + ( xy - zy) ]

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

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

13 tháng 8 2020

(x - y).z3 + (y - z).x3 + (z - x).y3

= z3(x - y) + x3y - x3z + y3z - xy3

= z3(x - y) + xy(x2 - y2) - z(x3 - y3)

= z3(x - y) + xy(x - y)(x + y) - z(x - y)(x2 + xy + y2)

= (x - y)(z3 + x2y + xy2 - x2z - xyz - y2z)

= (x - y)[z(z2 - x2) + xy(x - z) + y2(x - z)]

= (x - y)[z(z - x)(z  + x) - xy(z- x) - y2(z - x)]

= (x - y)(z - x)(z2 + xz - xy - y2)

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

= (x  - y)(z - x)(y - z)(y + z - x)

23 tháng 7 2021

( x + y + z)3 - x3 - y3 - z3=x3+y3+z3+3(a+b)(a+c)(b+c)- x3 - y3 - z3

                                              = 3(a+b)(b+c)(a+c)

10 tháng 11 2021

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)

a: (x+y+z)^3-x^3-y^3-z^3

=(x+y+z-x)(x^2+2xy+y^2-x^2-xy-xz+z^2)-(y+z)(y^2-yz+z^2)

=(x+y)(y+z)(x+z)

b: x^3+y^3+z^3=1

x+y+z=1

=>x+y=1-z

x^3+y^3+z^3=1

=>(x+y)^3+z^3-3xy(x+y)=1

=>(1-z)^3+z^3-3xy(1-z)=1

=>1-3z-3z^2-z^3+z^3-3xy(1-z)=1

=>1-3z+3z^2-3xy(1-z)=1

=>-3z+3z^2-3xy(1-z)=0

=>-3z(1-z)-3xy(1-z)=0

=>(z-1)(z+xy)=0

=>z=1 và xy=0

=>z=1 và x=0; y=0

A=1+0+0=1

10 tháng 11 2021

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)

27 tháng 10 2019

Câu hỏi của Lee Min Ho - Toán lớp 8 - Học toán với OnlineMath