Toán Lớp 8: Bài Tập:Phân tích :
a)N= $z^{2}$ – $y^{2}$ – 6xy – 9 $x^{2}$
b)P= $x^{3}$ +$y^{3}$+ $z^{3}$ – 3xyz
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 8: Bài Tập:Phân tích :
a)N= $z^{2}$ – $y^{2}$ – 6xy – 9 $x^{2}$
b)P= $x^{3}$ +$y^{3}$+ $z^{3}$ – 3xyz
Comments ( 2 )
=z^2-(y^2+6xy+9x^2)
=z^2-(3x+y)^2
=(z-3x-y)(z+3x+y)
b)x^3+y^3+z^3-3xyz
=x^3+3x^2y+3xy^2+y^3+z^3-3x^2y-3xy^2-3xyz
=(x+y)^3+z^3-3xy(x+y+z)
=(x+y+z)[(x+y)^2-(x+y)z+z^2]-3xy(x+y+z)
=(x+y+z)(x^2+2xy+y^2-xz-yz+z^2-3xy)
=(x+y+z)(x^2+y^2+z^2-xy-yz-zx)