Why does $\displaystyle Ax + By - C = 0$ ?

Why does an equation for a line have to equal zero?

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- Aug 31st 2009, 11:02 PM #1

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- Aug 31st 2009, 11:12 PM #2

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- Sep 1st 2009, 03:03 AM #3

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7x = 21

7x - 21 = 0

7 = $\displaystyle \dfrac{21}{x}$

x = $\displaystyle \dfrac{21}{7}$

You can write the equation in may ways, but when you have the equation equated to zero, it is called "standard form"

Someone called it that, and others must have thought it more appropriate than "subtract all of the variables on the LHS (or RHS) from the other side and simplify" form.