ta có: 

1C

2C

3D

4B

1 c

2c

3d

4b

câu hỏi đúng 100%

\(x+\frac{3}{5}=\frac{5x+3}{5}\)

\(y-\frac{2}{4}=y-\frac{1}{2}=\frac{2y-1}{2}\)

\(z+\frac{y}{x}=\frac{xz+y}{x}\)

Mà \(x+\frac{3}{5}=y-\frac{2}{4}=z+\frac{y}{x}\)

\(\Rightarrow\frac{5x+3}{5}=\frac{2y-1}{2}=\frac{xz+y}{x}\)

\(\Rightarrow\frac{5x+3}{5}=\frac{2y-1}{2}\)

\(\Leftrightarrow2\left(5x+3\right)=5\left(2y-1\right)\)

\(10x+6=10y-5\)

\(10x+6-10y+5=0\)

\(10\left(x-y\right)+11=0\)

\(x-y=-\frac{11}{10}\)

\(\Rightarrow x=-\frac{11}{10}+y\)

Lại có : \(xy=70\)

\(\Rightarrow-\frac{11}{10}+y.y=70\)

\(y\left(-\frac{11}{10}+1\right)=70\)

\(-\frac{1}{10}y=70\)

\(y=70:\left(-\frac{1}{10}\right)\)

\(y=70.\left(-10\right)\)

\(y=-700\)

\(\Rightarrow x.\left(-700\right)=70\)

\(x=-\frac{1}{10}\)

\(5^{2x-7}=5^{13}\)

\(\Rightarrow2x-7=13\)

\(\Rightarrow2x=13+7\)

\(\Rightarrow2x=20\)

\(\Rightarrow x=20:2\)

\(\Rightarrow x=10\)

\(\frac{5}{2}\left(x-\frac{3}{5}\right)-\frac{1}{10}=x-3\)

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

\(\frac{5}{2}x-\frac{15}{10}-\frac{1}{10}=x-2\)

\(\frac{5}{2}x-\frac{7}{5}=x-2\)

\(\frac{5}{2}x-\frac{7}{5}-x+2=0\)

\(x\left(\frac{5}{2}-1\right)-\frac{7}{5}+\frac{10}{5}=0\)

\(\frac{3}{2}x+\frac{3}{5}=0\)

\(\frac{3}{2}x=\left(-\frac{3}{5}\right)\)

\(x=\left(-\frac{3}{5}\right):\frac{3}{2}\)

\(x=\left(-\frac{3}{5}\right).\frac{2}{3}\)

\(x=\left(-\frac{2}{5}\right)\)

ab200

\(\left|x\right|\ge0\)

\(\Rightarrow\frac{-1}{\left|x\right|+1}\ge\frac{-1}{0+1}=-1\)

Dấu bằng khi x = 0

\(\frac{9^5.27^3}{3^{18}}\)

\(=\frac{\left(3^2\right)^5.\left(3^3\right)^3}{3^{18}}\)

\(=\frac{3^{10}.3^9}{3^{18}}\)

\(=\frac{3^{19}}{3^{18}}=3\)

9 mũ 5 với 27 mũ 3 nhé