a)
[tex]x^{6}+6x^{5}+9x^{4} = 0\\\\x^{4}(x^{2}+6x+9) = 0\\\\x^{4}(x+3)^{2} = 0\\\\x^{4} = 0 \ \vee \ (x+3)^{2} = 0\\\\x = 0 \ \vee \ x+3 = 0\\\\x = 0 \ \vee \ x = -3\\\\x \in \{-3,0\}[/tex]
b)
[tex]x^{5}=-8x^{2}\\\\x^{5}+8x^{2} = 0\\\\x^{2}(x^{3}+8) = 0\\\\x^{2}(x^{3}+2^{3}) = 0\\\\x^{2} = 0 \ \vee \ x+2 = 0\\\\x = 0 \ \vee \ x = -2\\\\x \in\{-2,0\}[/tex]
