Bonjour Mademoiselle123
[tex](2x-\dfrac{3}{4})(3x^2-4x)=0\\\\2x-\dfrac{3}{4}=0\ \ ou\ \ 3x^2-4x=0\\\\2x=\dfrac{3}{4}\ \ ou\ \ x(3x-4)=0\\\\x=\dfrac{3}{8}\ \ ou\ \ x=0\ \ ou\ \ 3x-4=0\\\\x=\dfrac{3}{8}\ \ ou\ \ x=0\ \ ou\ \ 3x=4\\\\\boxed{x=\dfrac{3}{8}\ \ ou\ \ x=0\ \ ou\ \ x=\dfrac{4}{3}}[/tex]
[tex](\dfrac{25}{4}x^2-1)(x+2)=0\\\\(\dfrac{25}{4}x^2-1^2)(x+2)=0\\\\(\dfrac{5}{2}x-1)(\dfrac{5}{2}x+1)(x+2)=0\\\\\dfrac{5}{2}x-1=0\ \ ou\ \ \dfrac{5}{2}x+1=0\ \ ou\ \ x+2=0\\\\\dfrac{5}{2}x=1\ \ ou\ \ \dfrac{5}{2}x=-1\ \ ou\ \ x=-2\\\\\boxed{x=\dfrac{2}{5}\ \ ou\ \ x=-\dfrac{2}{5}\ \ ou\ \ x=-2}[/tex]
