Toán Lớp 8: a) 3x²y²z–12xy²z b) y²–18y +81 c)zx³–zy³+x–y Giúp em với ạ em cảm ơn

Question

Toán Lớp 8:  a) 3x²y²z–12xy²z b) y²–18y +81 c)zx³–zy³+x–y Giúp em với ạ em cảm ơn

minhtamnguyet88 · Answer

a) 3x&sup2;y&sup2;z&ndash;12xy&sup2;z      = 3xy&sup2;z (x- 4)      b) y&sup2;&ndash;18y +81      = y&sup2; - 2 &times; 9y+ 9&sup2;     =(y-9)&sup2;     c)zx&sup3;&ndash;zy&sup3;+x&ndash;y     = z(x&sup3;-y&sup3;) + ( x-y)   =z(x-y)(x&sup2;+xy+y&sup2;)+(x-y)   =(x-y)[z(x&sup2;+xy+y&sup2;)+1]   =(x-y)(zx&sup2;+zxy+zy&sup2;+1)

hiennhi98 · Answer

a) 3x^2y^2z- 12xy^2z   = 3xy^z (x-4)   ______________________________   b)y^2- 18y+81   = y^2- 2.y.9+ 9^2   = (y-9)^2   ______________________________   c) zx^3- zy^3+x-y   = x(x^3- y^3)+x-y   = z(x-y)(x^2+xy+y^2)+x-y   = (x-y)[z(x^2+xy+y^2)+1]   = (x-y)(x^2z+ xyz+ y^2z+1)   $ text{B1: Đặt z l&agrave; nh&acirc;n tử chung}$   $ text{B2: D&ugrave;ng HĐT a&sup3;- b&sup3;= (a-b)(a&sup2;+ ab+b&sup2;)}$   $ text{B3: Đặt $x-y$ l&agrave; nh&acirc;n tử chung}$   $ text{B4: Nh&acirc;n ph&aacute; ngoặc}$