[tex]1. \\\\x^3-6x^2-12x+72=0\\x^2(x-6)-12(x-6)=0\\(x^2-12)(x-6)=0\\x^2-12=0\\x^2=12\\x=\sqrt{12}=2\sqrt3 \text{ v } x=-2\sqrt3\\\\x-6=0\\x=6\\\\\text{Odp. } x=6 \text{ v } x=2\sqrt3 \text{ v } x=-2\sqrt3[/tex]
[tex]2. \\\\x^2(x+5)(2x^2+3)=0\\\\x^2=0\\x=0\\\\x+5=0\\x=-5\\\\2x^2+3=0\\2x^2=-3 /:2\\x^2=-\frac32 - \text{ urojona}\\\\\text{Odp. } x=0 \text{ v } x=-5[/tex]
[tex]3. \\\\-x^4-9x^2+10=0\\t=x^2\\-t^2-9t+10=0\\\Delta=(-9)^2-4*(-1)*10=81+40=121\\\sqrt{\Delta}=11\\t_1=\frac{9-11}{-2}=\frac{-2}{-2}=1\\t_2=\frac{9+11}{-2}=\frac{20}{-2}=-10\\\\x_1=\sqrt{t_1}=\sqrt{1}=1 \text{ v } x=-1\\x_2=\sqrt{t_2}=\sqrt{-10} - \text{ urojona}\\\\Odp. x=1 \text{ v } x=-1[/tex]
