Hi

I have these two expressions

$\displaystyle A+B=D$ and $\displaystyle D=\frac{\text{i}2kA}{\text{i}k-\alpha}$

I need to find $\displaystyle B$, so I substitute $\displaystyle D$ into the first expression. The problem is I don't know how to get it into the form below

$\displaystyle B=A\frac{(\text{i}k+\alpha)}{(\text{i}k-\alpha)}$

Thanks