Exercício sobre inequação do segundo grau II

Resolver em $\,{\rm I\!R}\,$ as inequações a seguir:

$\,x^4\,-\,10x^2\,+\,9\,\leqslant\,0\,$

$\,x^4\,-\,3x^2\,-\,9\,\gt\,0\,$

$\,x^4\,+\,8x^2\,-\,9\,\lt\,0\phantom{X}$

$\,2x^4\,-\,3x^2\,+\,4\,\lt\,0\,$

$\,x^6\,-\,7x^3\,-\,8\,\geqslant\,0\phantom{X}$

$\,3x^4\,-\,5x^2\,+\,4\,\gt\,0\,$

resposta: a) $\,\mathbb{S}\,=\,\lbrace x\,\in\,{\rm I\!R}\;|\;-3\,\leqslant\,x\,\leqslant\,-1\,\phantom{X}{\text ou}\phantom{X}1\,\leqslant\,x\,\leqslant\,3\rbrace$
b) $\,\mathbb{S}\,=\,\lbrace x\,\in\,{\rm I\!R}\;|\;x\,\lt\,-2\,\phantom{X}{\text ou}\phantom{X}x\,\gt\,2\rbrace$
c) $\,\mathbb{S}\,=\,\lbrace x\,\in\,{\rm I\!R}\;|\;-1\,\lt\,x\,\lt\,1\rbrace$
d) $\,\mathbb{S}\,=\,\varnothing\,$
e) $\,\mathbb{S}\,=\,\lbrace x\,\in\,{\rm I\!R}\;|\;x\,\leqslant\,-1\,\phantom{X}{\text ou}\phantom{X}x\,\geqslant\,2\rbrace$
a) $\,\mathbb{S}\,=\,{\rm I\!R}\,$

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