1) [tex] \frac{a^{3}-1 }{a^{2}+a+1 } [/tex]
2) [tex] \frac{x^{2}-m }{m*(x+m)}- \frac{x}{m} [/tex]
3) [tex] \frac{1}{2x}+ \frac{4}{x+2} [/tex]
4) [tex]2c- \frac{2c}{c-1} [/tex]