Stuck on some simple algebra in the very first example of the first lecture (talk about rusty!).
I understand the algebra all the way until the end where:

(1/Δx)[(x0-(x0+Δx))/((x0+Δx)x0)] =
(1/Δx)[(-Δx/((x0+Δx)x0)]

How does the numerator reduce to -Δx?

Wouldn't x0-(x0+Δx) = Δx?

Question

Stuck on some simple algebra in the very first example of the first lecture (talk about rusty!).
I understand the algebra all the way until the end where:

(1/Δx)[(x0-(x0+Δx))/((x0+Δx)x0)] = 
(1/Δx)[(-Δx/((x0+Δx)x0)]

How does the numerator reduce to -Δx?

Wouldn't x0-(x0+Δx) = Δx?

anonymous · Answer

After some thought, I believe I answered my own question. The minus sign is transitive and is reduced to x0 - x0 - Δx.

phi · Answer

you "distribute" the minus sign
-1*(a +b) = -1*a + -1*b = -a - b