2.3a Lösning 6a
Från Mathonline
\[ \lim_{x \to 3}\,\, {x^2\,-\,9 \over 7\,x\,-\,21} \, = \, \lim_{x \to 3}\, {(x + 3) \cdot {\color{Red} {(x-3)}} \over 7 \cdot {\color{Red} {(x-3)}}} \, = \, \lim_{x \to 3} \, {x + 3 \over 7} \, = \, {3 + 3 \over 7} \, = \, {6 \over 7} \]
