giải bất phương trình
a/\(\frac{x^4-x^2}{x^2+5x+6}\le0\)
b/\(\frac{4x^2+3x-1}{x^2+5x+7}>0\)
c/\(\frac{x^4+x^2+1}{x^2-4x-5}\le0\)
d/\(\frac{-2x^2+7x+7}{x^2-3x-10}\le-1\)
e/\(\frac{2\left(x-4\right)}{\left(x-1\right)\left(x-7\right)}\ge\frac{1}{x-2}\)