\(\left(3x-2\right)^2-4x\left(x-3\right)=\left(5x+1\right)\left(x-4\right).\)
\(\Leftrightarrow9x^2-12x+4-4x^2+12x=5x^2-20x+x-4\)
\(\Leftrightarrow9x^2-12x+4-4x^2+12x=5x^2-20x+x-4\)
\(\Leftrightarrow19x=-8\)
\(\Rightarrow x=-\frac{8}{19}\)
\(\left(x+3\right)\left(3x-1\right)=9x^2-1\)
\(\Leftrightarrow\left(x+3\right)\left(3x-1\right)=\left(3x-1\right)\left(3x+1\right)\)
\(\Leftrightarrow\left(x+3\right)\left(3x-1\right)-\left(3x-1\right)\left(3x+1\right)=0\)
\(\Leftrightarrow\left(3x-1\right)\left(x+3-3x-1\right)=0\)
\(\Leftrightarrow\left(3x-1\right)\left(2-2x\right)=0\)
Th1 : 3x - 1 = 0
=> x = 1/3
Th2: 2 - 2x = 0
=> x = 1
