[tex]x^4-31x^2-30x=0\\x(x^3-31x-30)=0\\\\x=0\\\\x^3-31x-30=0\\x^3-x-30x-30=0\\x(x^2-1)-30(x+1)=0\\(x+1)(x(x-1)-30))=0\\(x+1)(x^2-x-30)=0\\\\x+1=0\\x=-1\\\\x^2-x-30=0\\x^2+5x-6x-30=0\\x(x+5)-6(x+5)=0\\(x-6)(x+5)=0\\x=6 \vee x=-5\\\\\boxed{x\in\{-5,-1,0,6\}}[/tex]
