1- Effectuez: $\frac{7}{a^2}+{1}{a}-3$
$\frac{7-2a^2}{a^2}$	$\frac{7a+a^2-3a^3}{a^3}$	$\frac{7+a-3a^2}{a^2}$

2- Effectuez: $\frac{2}{b-3}-\frac{1}{b-5}$
$\frac{2(b-5)-(b-3)}{(b-3)(b-5)}$	$\frac{b-13}{(b-3)(b-5)}$	$\frac{b-7}{(b-3)(b-5)}$

3- Effectuez: $\frac{x-y}{x+y}+\frac{x+y}{x-y}$
$\frac{2(x+y)}{x-y}$	$\frac{(x-y)^2+(x+y)^2}{(x+y)(x-y)}$	$\frac{2(x^2+y^2)}{x^2-y^2)}$	$(x-y)(x+y)$

4- Effectuez: $\frac{4}{m-3}+\frac{3}{m^2-9}$
$\frac{4(m+3)+3}{(m-3)(m3)}$	$\frac{4m^2+3m-45}{(m-3)(m^2-9)}$	$\frac{4m^2+3m-45}{m^3-27}$	$\frac{4m+15}{m^2-9}$

5- Effectuez: $\frac{3a}{5bc}+\frac{d}{15b}+\frac{7a^2d}{3b^2c^3}$
$\frac{9abc^2+bc^3d+35a^2d}{15b^2c^3}$	$\frac{27ab^3c^3+3b^3c^4d+105a^2b^2cd}{45b^4c^4}$	$\frac{3a+bc^2d+35a^2d}{5}$