a)12x-9-4x2=0
\(\Leftrightarrow-\left(2x-3\right)^2=0\)
\(\Leftrightarrow2x-3=0\\ \Leftrightarrow x=\dfrac{3}{2}\)
b) x+x2-x3-x4 =0
\(\Leftrightarrow x\left(1-x^2\right)+x^2\left(1-x^2\right)=0\)
\(\Leftrightarrow x\left(1-x\right)\left(x+1\right)^2=0\)
=> x=0 hoặc x=1 hoặc x=-1
c)