Problem
\( \frac{x^{2}+10 x+21}{x^{2}-9} \)
Solution
Step 1 ：\( \frac{x^{2}+10x+21}{x^{2}-9} = \frac{(x+3)(x+7)}{(x-3)(x+3)} \)
Step 2 ：\( \frac{(x+3)(x+7)}{(x-3)(x+3)} = \frac{x+7}{x-3} \)
Step 1 ：\( \frac{x^{2}+10x+21}{x^{2}-9} = \frac{(x+3)(x+7)}{(x-3)(x+3)} \)
Step 2 ：\( \frac{(x+3)(x+7)}{(x-3)(x+3)} = \frac{x+7}{x-3} \)
