For this case we have the following fraction:
[tex] \frac{\frac{1}{a} - \frac{1}{b}}{\frac{1}{a}+\frac{1}{b}} [/tex]
To find the common denominator, what we must do is rewrite the fraction.
For this, we subtract fractions in the numerator and the sum of fractions in the denominator.
We have then:
[tex] \frac{\frac{b-a}{ab}}{\frac{b+a}{ab}} [/tex]
We observe that the common denominator is given by the product:
[tex] ab [/tex]
Answer:
the common denominator is:
D)ab
