Tìm x, biết

$$\begin{gathered} bài 3 tìm x biết \\ 1) x(5+3x)-(x+1\left)\right(3x-2)=6 \\ 2) x(x+3)-2x-6=0 \\ 3) (x^4-2x^2-8):(x-2)=0 \\ 4) {(2x+\frac{1}{2})}^2-{(1-2x)}^2=25) (3x^3+x^2-13x+5) : (x^2+2x -1)=10 \\ 6)\frac{x^2-4x}{x^2-8x+16}=0 \end{gathered}$$