Originally Posted by

**fcabanski** Please explain it. In the second example I showed, there was no setting k=nc.

Why is K=-10c set? How do you know to do it before you have the solution?

Forget your second example. It was just a red herring.

Let me put it this way. The equation of the line can be written as either

$\displaystyle 10y+9x-57\ =\ 0$

or

$\displaystyle y\ =\ -\frac9{10}x+\frac{57}{10}$

They are the same. Yes? If you write it the first way, the constant term appears as $\displaystyle -57.$ If the second way, it appears as $\displaystyle \frac{57}{10}.$ Does this now make sense?