[tex]a) x^3-6x^2-12x+72=0\\x^2(x-6)-12(x-6)=0\\(x^2-12)(x-6)=0\\x^2=12~\vee~x=6\\x=-2\sqrt{3} ~\vee~x=2\sqrt{3}~\vee~x=6[/tex]
[tex]b)x^2(x+5)(2x^2+3)=0\\x^2=0~\vee~x=-5~\vee~x^2=-\frac{3}{2} \\x=0~\vee~x=-5~\vee~x\in\oslash[/tex]
[tex]c)-x^4-9x^2+10=0,~~t=x^2~\land~t\geq 0\\-t^2-9t+10=0\\\Delta=81-4(-10)=121\\\sqrt{\Delta} =11\\t_1=\frac{9+11}{-2} =-10< 0\\t_2=\frac{9-11}{-2} =1>0\\\\t=1\\x^2=1\\x=1~\vee~x=-1[/tex]
