g: \(x^2-3x+2=0\)
=>(x-1)(x-2)=0
=>x=1 hoặc x=2
i: \(x^4+x^2+6x-8=0\)
\(\Leftrightarrow x^4-x^3+x^3-x^2+2x^2-2x+8x-8=0\)
\(\Leftrightarrow\left(x-1\right)\left(x^3+x^2+2x+8\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left[\left(x+2\right)\left(x^2-2x+4\right)+x\left(x+2\right)\right]=0\)
\(\Leftrightarrow\left(x-1\right)\left(x+2\right)\left(x^2-x+4\right)=0\)
=>x=1 hoặc x=-2
h) \(x^3-8x^2+21x-18=0\)
\(\Leftrightarrow x^3-2x^2+6x^2-12x+9x-18=0\)
\(\Leftrightarrow x^2\left(x-2\right)+6x\left(x-2\right)+9\left(x-2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x^2+6x+9\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x+3\right)^2=0\)
\(\Leftrightarrow x-2=0\) hay \(x+3=0\)
\(\Leftrightarrow x=2\) hay \(x=-3\)