(√7 + Х)- (√ 7-Х) / 5x Найти пределы функции lim x->0

Решите задачу:

$= \lim_{x \to 0} { \frac{ \sqrt{7+x}- \sqrt{7-x}}{5x} } = \\ = \lim_{x \to 0} { \frac{ (\sqrt{7+x}- \sqrt{7-x})*(\sqrt{7+x}+ \sqrt{7-x})}{5x*(\sqrt{7+x}+ \sqrt{7-x})} } = \\ = \lim_{x \to 0} { \frac{ ({7+x- 7+x})}{5x*(\sqrt{7+x}+ \sqrt{7-x})} } = \\ = \lim_{x \to 0} { \frac{ 2x}{5x*(\sqrt{7+x}+ \sqrt{7-x})} } = \\ = \lim_{x \to 0} { \frac{ 2}{5*(\sqrt{7+x}+ \sqrt{7-x})} } = \frac{2}{5*2* \sqrt{7} } = \frac{1}{5*\sqrt{7}}$