To isolate $\frac{1}{R_{eq}}$ in the equation

$\frac{1}{R_{eq}} = \frac{1}{r_1} + \frac{1}{r_2},$

no additional steps are necessary because $\frac{1}{R_{eq}}$ is already isolated. The equation shows that $\frac{1}{R_{eq}}$ is equal to the sum of $\frac{1}{r_1}$ and $\frac{1}{r_2}$.

Would you like further details or have any questions?

Here are 5 related questions to consider:

1. How can you find $R_{eq}$ from the equation $\frac{1}{R_{eq}} = \frac{1}{r_1} + \frac{1}{r_2}$?
2. What happens to $R_{eq}$ if $r_1$ and $r_2$ are equal?
3. How does the equivalent resistance $R_{eq}$ change if another resistor $r_3$ is added in parallel?
4. Can this formula be extended to more than two resistors? How?
5. How would you approach solving $R_{eq}$ if $r_1$ and $r_2$ are given in different units?

Tip: Remember that in parallel circuits, the equivalent resistance is always less than the smallest individual resistance.