# General algerbra question

1. May 31, 2009

2. Jun 1, 2009

### CompuChip

Do you mean where they go from
Qc/(Qh-Qc) to (Qc/Qc)/(1-Qh/Qc)?

They simply divided both numerator and denominator by Qc. The goal here is to rewrite everything not in terms of Qh and Qc separately, but only in their ratio Qc/Qh (or Qh/Qc).

3. Jun 1, 2009

### Moo Of Doom

But they're clearly making a sign error when doing this. Luckily for them, they make the same sign error a second time, so the effects cancel. A correct derivation would be:

$$\frac{Q_C}{Q_H - Q_C} = \frac{1}{Q_H/Q_C - 1} = \frac{1}{T_H/T_C - 1} = \frac{T_C}{T_H - T_C}$$