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## Homework Statement

[/B]

I was reviewing this stuff and although I excelled at it once, I seem to forget some of it.

For example, please consider this:

## Homework Equations

[itex]R_C=\frac {R_1R_2} {R_1+R_2} + R_3[/itex]

Here's the correct formula for its error:

[itex]\Delta R_C=\frac {R_1R_2} {R_1+R_2} \left[ \frac {\Delta R_1} {R_1} +\frac {\Delta R_2} {R_2}

+\frac {\Delta R_1 + \Delta R_2} {R_1+R_2}\right] + \Delta R_3[/itex]

While mine would be this and I don't know what happened to the [itex]\Delta R_3[/itex] in the formula above:

[itex]\Delta R_C=\frac {R_1R_2} {R_1+R_2} \left[ \frac {\Delta R_1} {R_1} +\frac {\Delta R_2} {R_2}

+\frac {\Delta R_1 + \Delta R_2} {R_1+R_2} + \frac {\Delta R_3} {R_3}\right][/itex]

Another equation is:

[itex]I_1=\frac {R_3V_1+R_2(V_1+V_2)} {R_1R_2+R_2R_3+R_3R_1}[/itex]

Which I don't know the correct solution to finding its error, but here's my attempt at a solution:

## The Attempt at a Solution

[itex]\Delta I_1= I_1 \left[ \frac {\Delta R_3 \Delta V_1+\Delta R_2 \Delta V_1+ \Delta R_2 \Delta V_2} {R_3V_1 + R_2(V_1+V_2)} + \frac {\Delta R_1 \Delta R_2+ \Delta R_2 \Delta R_3+ \Delta R_3 \Delta R_1} {R_1R_2+R_2R_3+R_3R_1}\right] [/itex]

Is this correct, if not, why?

Thank you in advance.