[tex]\displaystyle\bf\\\frac{4a^{2} +8}{a^{3} +1} -\frac{4}{a^{2} -a+1} -\frac{1}{a+1} =\\\\\\=\frac{4a^{2} +8}{(a +1)(a^{2}-a+1) } -\frac{4}{a^{2} -a+1} -\frac{1}{a+1} =\\\\\\=\frac{4a^{2} +8-4\cdot(a+1)-1\cdot(a^{2} -a+1)}{(a+1)(a^{2} -a+1)} =\\\\\\=\frac{4a^{2} +8-4a-4-a^{2}+a-1 }{(a+1)(a^{2} -a+1)} =\frac{3a^{2} -3a+3}{(a+1)(a^{2} -a+1)} =\\\\\\=\frac{3\cdot(a^{2} -a+1)}{(a+1)(a^{2} -a+1)} =\frac{3}{a+1} \\\\\\a=-0,2\\\\\\\frac{3}{a+1} =\frac{3}{-0,2+1} =\frac{3}{0,8} =3,75[/tex]