Question

giải pt sau: (x² -1) (x² +4x+3) =192

Answer 1

\(\Leftrightarrow\left(x-1\right)\left(x+1\right)\left(x+1\right)\left(x+3\right)=192\)

\(\Leftrightarrow\left(x^2+2x-3\right)\left(x^2+2x+1\right)=192\)

\(\Leftrightarrow\left(x^2+2x\right)^2-2\left(x^2+2x\right)-3-192=0\)

\(\Leftrightarrow\left(x^2+2x\right)^2-2\left(x^2+2x\right)-195=0\)

\(\Leftrightarrow\left(x^2+2x-15\right)\left(x^2+2x+13\right)=0\)

=>(x+5)(x-3)=0

=>x=3 hoặc x=-5