Late Sunday night poser

[Thomas Klemm]

(10-26-2024 08:13 PM)toml_12953 Wrote:  Since division is performed left to right, according to PEMDAS

As far as I know, PEMDAS is about operator precedence.
I guess that left associativity of subtraction is just assumed as given when chain calculations are introduced in primary school.
But given that both addition and subtraction are binary operation, an expression like \(8 - 3 + 5\) doesn't even make sense.
You'd have to use parentheses to either mean \((8 - 3) + 5 = 10\) or \(8 - (3 + 5) = 0\).
Defining subtraction to be left associative, allows to write expressions like these without parentheses:

\(
\frac{1}{1+x}=1-x+x^2-x^3+x^4-x^5+ \cdots \; (|x|<1)
\)