Algebraic fractions

Simplify $\frac{r^2-s^2}{4r^2+rs-5s^2}$   

•  $\frac{r+s}{4r+5s}$  

•  $\frac{r+s}{4r+5s};\ r\ne s$  

•  $\frac{r+s}{4r+5s};\ r\ne s;\ r\ne\frac{5s}{4}$  

• None of the above

Simplify $\frac{6a^3+10a^2}{36a^3-100a}$   

•  $\frac{a\left(3a+5\right)}{2\left(9a^2-25\right)}$  

•  $\frac{a\left(3a+5\right)}{2\left(3a-5\right)}$  

•  $\frac{a}{\left(3a-5\right)}$  

• None of the above

When x=____, $\frac{x^2-4}{x^2-4x+4}=0$   

Simplify $\frac{4a^2-b^2-2a+b}{\left(2a+b\right)^2-1}$   

•  $\frac{2a-b}{2a+b+1};b\ne1-2a;\ b\ne-\left(2a+1\right)$  

•  $\frac{\left(2a-b\right)\left(2a+b\right)-\left(2a-b\right)}{\left(2a+b-1\right)\left(2a+b+1\right)};b\ne1-2a;\ b\ne-\left(2a+1\right)$  

•  $\frac{\left(2a-b\right)\left(2a+b\right)+\left(2a-b\right)}{\left(2a+b-1\right)\left(2a+b+1\right)};b\ne1-2a;\ b\ne-\left(2a+1\right)$  

• None of the above

Solve $cx+dx=c^2-d^2$   for x.

•  $x=\frac{c^2-d^2}{c-d}$  

•  $x=c-d$  

•  $x=c^2-d^2$  

• None of the above