The given rational expression is,
[tex]\frac{7}{x+2}[/tex]The denominator of the expression becomes LCD (x+2)(x-7), multiply the numerator and denominator of the rational expression by (x-7).
[tex]\begin{gathered} \frac{7}{x+2}=\frac{7}{x+2}(\frac{x-7}{x-7}) \\ =\frac{7(x-7)}{(x+2)(x-7)} \end{gathered}[/tex]In the rational expression 2/(x-7), the denominator (x-7) becomes the LCD (x+2)(x-7) if the numerator and denominator of the expression is multipied by (x+2).
[tex]\begin{gathered} \frac{2}{x-7}=\frac{2}{(x-7)}(\frac{x+2}{x+2}) \\ =\frac{2(x+2)}{(x+2)(x-7)} \end{gathered}[/tex]