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16 tháng 4 2020

có ai giúp minh vs nhanh lên nha 

27 tháng 12 2015

a,\(\frac{2x^2+4x}{x+2}\)=\(\frac{2x\left(x+2\right)}{x+2}\)\(=2x\)

b, \(\frac{3x}{2x+4}\)=\(\frac{3x^2-6x}{2\left(x+2\right)\left(x-2\right)}\)

\(\frac{x+3}{x^2+4}\)=\(\frac{2x+6}{2\left(x-2\right)\left(x+2\right)}\)

tick mình nhé!!

b)\(\frac{10}{x + 2} ; \frac{5}{2 x - 4} ; \frac{1}{6 - 3 x}\)


Giải:

a)

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

Mẫu chung: \(\left(\right. x - 1 \left.\right) \left(\right. x^{2} + x + 1 \left.\right)\)

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


b)

\(2 x - 4 = 2 \left(\right. x - 2 \left.\right) , 6 - 3 x = 3 \left(\right. 2 - x \left.\right) = - 3 \left(\right. x - 2 \left.\right)\)

Mẫu chung:

\(6 \left(\right. x + 2 \left.\right) \left(\right. x - 2 \left.\right)\) \(\frac{60 \left(\right. x - 2 \left.\right)}{6 \left(\right. x + 2 \left.\right) \left(\right. x - 2 \left.\right)} ; \frac{15 \left(\right. x + 2 \left.\right)}{6 \left(\right. x + 2 \left.\right) \left(\right. x - 2 \left.\right)} ; - \frac{2 \left(\right. x + 2 \left.\right)}{6 \left(\right. x + 2 \left.\right) \left(\right. x - 2 \left.\right)}\)

Bài 2:

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

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

18 tháng 11 2018

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:

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

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

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