Ta có : ( x2 - 1 )( x2 + 4x + 3 ) = 0
\(\Leftrightarrow\)( x - 1 )( x + 1 )[ ( x2 + 4x + 4 ) - 1 ] = 0
\(\Rightarrow\)( x - 1 )( x + 1 )[ ( x + 2 )2 - 12 ] = 0
\(\Rightarrow\)( x - 1 )( x + 1 )( x + 2 - 1 )( x + 2 + 1 ) = 0
\(\Rightarrow\)( x - 1 )( x + 1 )( x + 1 )( x + 3 ) = 0
\(\Rightarrow\)( x - 1 )( x + 1 )2( x + 3 ) = 0
\(\Rightarrow\)x - 1 = 0 hoặc ( x + 1 )2 = 0 hoặc x + 3 = 0
\(\Rightarrow\)x = 1 hoặc x = - 1 hoặc x = - 3
Vậy : x = 1 hoặc x = - 1 hoặc x = - 3
(x^2-1)(x^2+4x+3)=0
(x-1)(x+1)(x^2+3x+x+3)=0
(x-1)(x+1)[ x(x+1)+3(x+1)]=0
(x-1)(x+1)(x+3)(x+1)=0
x-1=0 hoặc x+1=0 hoặc x+3=0
=> x=1;-1;-3
