Toán Lớp 8: a) x^2-xy+x-y
b)xz+yz-5(x+y)
c)3x^2+6xy+3y^2-3z^2
Giúp mik trl nhanh vs huhu :<
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Toán Lớp 8: a) x^2-xy+x-y
b)xz+yz-5(x+y)
c)3x^2+6xy+3y^2-3z^2
Giúp mik trl nhanh vs huhu :<
Comments ( 2 )
$\rm a)\\x^2-xy+x-y\\=(x^2-xy)+(x-y)\\=x.(x-y)+(x-y)\\=(x+1)(x-y)\\b)\\xz+yz-5.(x+y)\\=(xz+yz)-5.(x+y)\\=z.(x+y)-5.(x+y)\\=(z-5)(x+y)\\c)\\3x^2+6xy+3y^2-3z^2\\=3.(x^2+2xy+y^2-z^2)\\=3.[(x+y)^2-z^2]\\=3.(x+y-z)(x+y+z)\\\text{Áp dụng hằng đẳng thức }\\A^2+2AB+B^2=(A+B)^2\\A^2-B^2=(A-B)(A+B)$
=x(x-y) +(x-y)