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\(A=\left(\frac{1}{\sqrt{x}-2}+\frac{1}{\sqrt{x}+2}\right):\frac{5x}{x-5}\)

\(=\left(\frac{\sqrt{x}+2}{x-4}+\frac{\sqrt{x}-2}{x-4}\right):\frac{5x}{x-5}\)

\(=\frac{2\sqrt{x}}{x-4}.\frac{x-5}{5x}=\frac{2\sqrt{x}\left(x-5\right)}{5x^2-20x}\)

5x³ + 38x² + 19x - 14

= ( 5x³ + 35x² ) + ( 3x² + 21x ) - ( 2x + 14 )

= 5x² ( x + 7 ) + 3x ( x + 7 ) - 2 ( x + 7 )

= ( x + 7 ) ( 5x² + 3x - 2 ) 

= ( x + 7 ) [ ( 5x² - 2x ) + ( 5x - 2 ) ]

= ( x + 7 ) [ x ( 5x - 2 ) + ( 5x - 2 ) ]

= ( x + 7 ) ( x + 1 ) ( 5x - 2 )    

\(5x^3+38x^2+19x-4\)

\(=\left(5x^3+35x^2\right)+\left(3x^2+21x\right)-\left(2x+14\right)\)

\(=5x^2\left(x+7\right)+3x\left(x+7\right)-2\left(x+7\right)\)

\(=\left(5x^2+3x-2\right)\left(x+7\right)\)

\(=\left(5x^2-2x+5x-2\right)\left(x+7\right)\)

\(=\left[x\left(5x-2\right)+\left(5x-2\right)\right]\left(x+7\right)\)

\(=\left(x+1\right)\left(5x-2\right)\left(x+7\right)\)

loooooo

ok me good

Chọn A. Hàn Quốc

có nha

CHO MÌNH XIN

\(\frac{x-2}{5}+7=\frac{x+1}{3}-\frac{8-x}{10}\)

\(\Leftrightarrow\frac{x-2+35}{5}=\frac{10x+10}{30}-\frac{24-3x}{30}\)

\(\Leftrightarrow\frac{x+33}{5}=\frac{13x-14}{30}\Leftrightarrow\frac{6x+198}{30}=\frac{13x-14}{30}\)

Khử mẫu : \(6x+198=13x-14\)

\(\Leftrightarrow-7x=-14-198=212\Leftrightarrow x=-\frac{212}{7}\)

\(\frac{x-2}{5}+7=\frac{1+x}{3}-\frac{8-x}{10}\)

\(\Leftrightarrow\frac{x-2}{5}+\frac{35}{5}=\frac{10\left(1+x\right)}{30}-\frac{3\left(8-x\right)}{30}\)

\(\Leftrightarrow\frac{x-2+35}{5}=\frac{10+10x-24+3x}{30}\)

\(\Leftrightarrow\frac{x+33}{5}=\frac{13x-14}{30}\)

\(\Leftrightarrow\frac{6\left(x+33\right)}{30}=\frac{13x-14}{30}\)

\(\Leftrightarrow6x+198=13x-14\)

\(\Leftrightarrow6x-13x=-14-198\)

\(\Leftrightarrow-7x=-212\)

\(\Leftrightarrow x=\frac{212}{7}\)

Ta có:\(A=2^{2019}-2^{2018}-....-2^2-2\)

\(=2^{2019}-\left(2^{2018}+2^{2017}+....+2^2+2\right)\)

Xét \(M=2^{2018}+2^{2017}+...+2^2+2\)

\(\Rightarrow2M=2^{2019}+2^{2018}+...+2^3+2^2\)

\(\Rightarrow2M-M=\left(2^{2019}+2^{2018}+...+2^3+2^2\right)-\left(2^{2018}+2^{2017}+...+2^2+2\right)\)

\(\Rightarrow M=2^{2019}-2\)

\(\Rightarrow A=2^{2019}-\left(2^{2019}-2\right)\)

\(\Rightarrow A=2\)

Chắc là thế,cũng chẳng biết đúng hay sai