Question

[Ka Ly Nguyễn]

1. a) Tính 2x( 3x²+4xy )

b) Tìm x biết: x( x -1) + x - 1=0

c) Phân tích đa thức sau thành nhân tử: x²- xy - 3x +3y

2. Tính:

a) (x³+ 4x²+ x - 2) \(\div\) (x + 1)

b) \(\dfrac{x-3}{2x-2}+\dfrac{1}{x-1}\)

3. Tính:

\(\dfrac{1}{\left(x-y\right)\left(y-z\right)}+\dfrac{1}{\left(y-z\right)\left(z-x\right)}+\dfrac{1}{\left(z-x\right)\left(x-y\right)}\)

giúp mik vs ạ, cảm ơn nhìu!

Answer 1

[Trần Minh Hoàng]

1.

c) x² - xy - 3x + 3y

= (x² - xy) - (3x - 3y)

= x(x - y) - 3(x - y)

= (x - 3)(x - y)

Answer 2

[Trần Minh Hoàng]

3.

ĐKXĐ: \(x\ne y,y\ne z,z\ne x\)

Ta có:

\(\dfrac{1}{\left(x-y\right)\left(y-z\right)}+\dfrac{1}{\left(y-z\right)\left(z-x\right)}+\dfrac{1}{\left(z-x\right)\left(x-y\right)}=\dfrac{\left(z-x\right)+\left(x-y\right)+\left(y-z\right)}{\left(x-y\right)\left(y-z\right)\left(z-x\right)}=0\)