Bài 2:

a: \(\dfrac{1}{2x^3y}=\dfrac{6yz^3}{12x^3y^2z^3}\)

\(\dfrac{2}{3xy^2z^3}=\dfrac{2\cdot4x^2}{12x^3y^2z^3}=\dfrac{8x^2}{12x^3y^2z^3}\)

MTC : ( x - 1 )( x² + x + 1 )

Ta có : \(\frac{4x^2-3x+5}{x^3-1}=\frac{4x^2-3x+5}{\left(x-1\right)\left(x^2+x+1\right)}\)

\(\frac{2x}{x^2+x+1}=\frac{2x\left(x-1\right)}{\left(x-1\right)\left(x^2+x+1\right)}=\frac{2x^2-2x}{\left(x-1\right)\left(x^2+x+1\right)}\)

\(\frac{6}{x-1}=\frac{6\left(x^2+x+1\right)}{\left(x-1\right)\left(x^2+x+1\right)}=\frac{6x^2+6x+6}{\left(x-1\right)\left(x^2+x+1\right)}\)

Hnay mới học thì hnay trả lời nhá :P

\(\frac{4x^2-3x+5}{x^3-1};\frac{2x}{x^2+x+1}\)

Ta có : \(x^3-1=\left(x-1\right)\left(x^2+x+1\right)\)

\(x^2+x+1=x^2+x+1\)

MTC : \(\left(x-1\right)\left(x^2+x+1\right)\)

\(\frac{4x^2-3x+5}{x^3-1}=\frac{4x^2-3x+5}{\left(x-1\right)\left(x^2+x+1\right)}\)

\(\frac{2x}{x^2+x+1}=\frac{2x\left(x-1\right)}{\left(x-1\right)\left(x^2+x+1\right)}=\frac{2x^2-2x}{\left(x-1\right)\left(x^2+x+1\right)}\)

\(\frac{2x}{x^2+x+1};\frac{6}{x-1}\)

Ta có : \(x^2+x+1=x^2+x+1\)

\(x-1=x-1\)

MTC : \(\left(x^2+x+1\right)\left(x-1\right)=x^3-1\)

\(\frac{2x}{x^2+x+1}=\frac{2x\left(x-1\right)}{\left(x^2+x+1\right)\left(x-1\right)}=\frac{2x^2-2x}{x^3-1}\)

\(\frac{6}{x-1}=\frac{6\left(x^2+x+1\right)}{\left(x-1\right)\left(x^2+x+1\right)}=\frac{6x^2+6x+6}{x^3-1}\)

a) Tìm MTC: x3 – 1 = (x – 1)(x2 + x + 1)

Nên MTC = (x – 1)(x2 + x + 1)

Nhân tử phụ:

(x3 – 1) : (x3 – 1) = 1

(x – 1)(x2 + x + 1) : (x2 + x + 1) = x – 1

(x – 1)(x2+ x + 1) : 1 = (x – 1)(x2 + x + 1)

Qui đồng:

b) Tìm MTC: x + 2

2x – 4 = 2(x – 2)

6 – 3x = 3(2 – x)

MTC = 6(x – 2)(x + 2)

Nhân tử phụ:

6(x – 2)(x + 2) : (x + 2) = 6(x – 2)

6(x – 2)(x + 2) : 2(x – 2) = 3(x + 2)

6(x – 2)(x + 2) : -3(x – 2) = -2(x + 2)

Qui đồng:

a) MTC: \(12x^3y^3\)

\(\dfrac{3}{4x^3y^2}=\dfrac{3\cdot3y}{4x^3y^2\cdot3y}=\dfrac{9y}{12x^3y^3}\)

\(\dfrac{2}{3xy^3}=\dfrac{2\cdot4x^2}{3xy^3\cdot4x^2}=\dfrac{8x^2}{12x^3y^3}\)

b) MTC: \(x\left(x-3\right)^2\)

\(\dfrac{5}{x^2-6x+9}=\dfrac{5}{\left(x-3\right)^2}=\dfrac{5x}{x\left(x-3\right)^2}\)

\(\dfrac{3}{x^2-3x}=\dfrac{3}{x\left(x-3\right)}=\dfrac{3\left(x-3\right)}{x\left(x-3\right)^2}=\dfrac{3x-9}{x\left(x-3\right)^2}\)

Tìm MTC: \(x^3-1=\left(x-1\right)\left(x^2+x+1\right)\)

Nên \(MTC=\left(x-1\right)\left(x^2+x+1\right)\)

Nhân tử phụ: 

\(\left(x^3-1\right)\div\left(x^3-1\right)=1\)

\(\left(x-1\right)\left(x^2+x+1\right)\div\left(x^2+x+1\right)=x-1\)

\(\left(x-1\right)\left(x^2+x+1\right)\div1=\left(x-1\right)\left(x^2+x+1\right)\)

Quy đồng:

\(\frac{4x^2-3x+5}{x^3-1}=\frac{4x^2-3x+5}{\left(x-1\right)\left(x^2+x+1\right)}\)

\(\frac{1-2x}{x^2+x+1}=\frac{\left(x-1\right)\left(1-2x\right)}{\left(x-1\right)\left(x^2+x+1\right)}\)

\(-2=\frac{-2\left(x^3-1\right)}{\left(x-1\right)\left(x^2+x+1\right)}\)

\(\dfrac{1}{3x+xy}=\dfrac{1}{x\left(y+3\right)}=\dfrac{\left(x+y\right)^2}{x\left(y+3\right)\left(x+y\right)^2}\)

\(2x+2y=2\left(x+y\right)=\dfrac{2\left(x+y\right)\cdot x\left(y+3\right)\left(x+y\right)^2}{x\left(y+3\right)\left(x+y\right)^2}\)

\(\dfrac{1}{x^2+2xy+y^2}=\dfrac{3x+xy}{x\left(y+3\right)\left(x+y\right)^2}\)

cho mình hỏi là giữa khác phân số với nhua là phải có dấu như là công, trừ, nhân hay chia chứ?