20)\(\left(2x-3\right)^2=4x^2-8\)
\(\Leftrightarrow4x^2-12x+9-4x^2+8=0\)
\(\Leftrightarrow-12x+17=0\)
\(\Rightarrow x=\frac{17}{12}\)
21)\(x-\left(x+2\right)\cdot\left(x-3\right)=4-x^2\)
\(\Leftrightarrow x-x^2+3x-2x+6-4+x^2=0\)
\(\Leftrightarrow2x+2=0\)
\(\Rightarrow x=-1\)
22)\(3x-\left(x-3\right)\cdot\left(x+1\right)=6x-x^2\)
\(\Leftrightarrow3x-x^2-x+3x+3-6x+x^2=0\)
\(\Leftrightarrow-x+3=0\)
\(\Rightarrow x=3\)
23)\(\frac{3x}{4}=6\)
\(\Leftrightarrow3x=\frac{6\cdot4}{1}=24\)
\(\Rightarrow x=8\)
24)\(\frac{2x}{3}=8\)
\(\Leftrightarrow2x=\frac{8\cdot3}{1}=24\)
\(\Rightarrow x=12\)
25)\(\frac{3}{5}\cdot x=-12\)
\(\Leftrightarrow3x=\frac{-12\cdot5}{1}=-60\)
\(\Rightarrow x=-20\)
26)\(\frac{7}{2}\cdot x=-8\)
\(\Leftrightarrow7x=\frac{-8\cdot2}{1}=-16\)
\(\Rightarrow x=\frac{-16}{7}\)
27)\(7+\frac{5x}{3}=x-2\)
\(\Leftrightarrow\frac{21}{3}+\frac{5x}{3}=\frac{3x}{3}-\frac{6}{3}\)
\(\Leftrightarrow\frac{21+5x-3x+6}{3}=0\)
\(\Leftrightarrow\frac{27+2x}{3}=0\)
\(\Rightarrow27+2x=0\)
\(\Rightarrow x=\frac{-27}{2}\)
28)\(x+4=\frac{2}{5}\cdot x-3\)
\(\Leftrightarrow\frac{5x}{5}+\frac{20}{5}=\frac{2x}{5}-\frac{15}{5}\)
\(\Leftrightarrow\frac{5x+20-2x+15}{5}=0\)
\(\Leftrightarrow\frac{3x+35}{5}=0\)
\(\Rightarrow3x+35=0\)
\(\Rightarrow x=\frac{-35}{3}\)
29)\(1+\frac{x}{9}=\frac{4}{3}\)
\(\Leftrightarrow\frac{9}{9}+\frac{x}{9}=\frac{12}{9}\)
\(\Leftrightarrow\frac{9+x-12}{9}=0\)
\(\frac{-3+x}{9}=0\)
\(\Rightarrow-3+x=0\)
\(\Rightarrow x=3\)
30)\(4+\frac{x}{5}=\frac{5}{3}\)
\(\Leftrightarrow\frac{60}{15}+\frac{3x}{15}=\frac{25}{15}\)
\(\Leftrightarrow\frac{60+3x-25}{15}=0\)
\(\Leftrightarrow\frac{35+3x}{15}=0\)
\(\Rightarrow35+3x=0\)
\(\Rightarrow x=\frac{-35}{3}\)
tick mình nha:)))
1. x=2
2. x=10
3. x=5
4. x=7
