[tex] (3x+6)^{2}=9 x^{2}-2x+1=0 25x^{2}=81 [/tex] je ne comprends pas comment faire

Bonsoir,

[tex](3x+6)^{2}=9\\(3x+6)^{2}-9=0\\(3x+6)^{2}-3^2=0\\\ [(3x+6)+3][(3x+6)-3]=0\\(3x+6+3)(3x+6-3)=0\\(3x+9)(3x+3)=0\\3x+9=0\ \ ou\ \ 3x+3=0\\3x=-9\ \ ou\ \ 3x=-3\\x=-3\ \ ou\ \ x=-1\\\boxed{S=\{-3;-1\}}[/tex]

[tex]x^{2}-2x+1=0\\(x-1)^2=0\\x-1=0\\x=1\\\boxed{S=\{1\}}\\\\25x^{2}=81\\25x^{2}-81=0\\(5x)^{2}-9^2=0\\(5x+9)(5x-9)=0\\5x+9=0\ \ ou\ \ 5x-9=0\\5x=-9\ \ ou\ \ 5x=9\\x=-\dfrac{9}{5}\ \ ou\ \ x=\dfrac{9}{5}\\\\\boxed{S=\{-\dfrac{9}{5};\dfrac{9}{5}\}}[/tex]