exo7 824

$\displaystyle{1 \over a^2+x^2}$.

${1 \over{(1+x^2)}^2}$.

$\displaystyle{x^3 \over x^2-4}$.

$\displaystyle{4x \over{(x-2)}^2}$.

$\displaystyle{1 \over x^2+x+1}$.

$\displaystyle{1 \over{(t^2+2t-1)}^2}$.

$\displaystyle{3t+1 \over{(t^2-2t+10)}^2}$.

$\displaystyle{3t+1 \over{t^2-2t+10}}$.

$\displaystyle{ 1 \over{t^3+1}}$.

$\displaystyle{x^3+2 \over{(x+1)}^2}$.

$\displaystyle{x+1 \over{x{(x-2)}^2}}$.

$\displaystyle{(x^2-1)(x^3+3) \over2x+2x^2}$.

$\displaystyle{x^2 \over{{(x^2+3)}^3 (x+1)}}$.

$\displaystyle{x^7+x^3-4x-1 \over x{(x^2+1)}^2}$.

$\displaystyle{3x^4-9x^3+12x^2-11x+7\over(x-1)^3(x^2+1)}$.