b: \(\Leftrightarrow\left(x^2+3x+2\right)\left(x^2+3x-18\right)=-36\)
\(\Leftrightarrow\left(x^2+3x\right)^2-16\left(x^2+3x\right)=0\)
\(\Leftrightarrow\left(x^2+3x\right)\left(x^2+3x-16\right)=0\)
hay \(x\in\left\{0;-3;\dfrac{-3+\sqrt{73}}{2};\dfrac{-3-\sqrt{73}}{2}\right\}\)
c: \(\Leftrightarrow6x^4-18x^3-17x^3+51x^2+11x^2-33x-2x+6=0\)
\(\Rightarrow\left(x-3\right)\left(6x^3-17x^2+11x-2\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(6x^3-12x^2-5x^2+10x+x-2\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(x-2\right)\left(6x^2-5x+1\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(x-2\right)\left(3x-1\right)\left(2x-1\right)=0\)
hay \(x\in\left\{3;2;\dfrac{1}{3};\dfrac{1}{2}\right\}\)
d: \(\Leftrightarrow\left(x-1\right)^2\cdot\left(x^2+3x+1\right)=0\)
hay \(x\in\left\{1;\dfrac{-3+\sqrt{5}}{2};\dfrac{-3-\sqrt{5}}{2}\right\}\)
