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# help

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If a > 0 and
$$a - \frac{1}{a} = \frac{5}{6},$$
then

$$a + \frac{1}{a} = \ ?$$

Jun 25, 2020

#1
+601
+2

$$a-\frac{1}{a}=\frac{5}{6}$$

Multiply a on both sides:

$$a^2-\frac{5}{6}a-1=0$$

Using the quadratic formula, ($$x = {-b \pm \sqrt{b^2-4ac} \over 2a}$$) you get two roots. One is positive, one is negative. Use the positive one because a > 0.

That root is $$\boxed{\frac{13}{6}}$$

Jun 25, 2020
edited by amazingxin777  Jun 25, 2020
edited by amazingxin777  Jun 25, 2020