Missing multiplication symbol
It's common to omit a multiplication symbol:
\(ab = a \times b\)
But sometimes it's not as clear:
Does \( a(b+1) = a \times (b+1)\), or is \(a\) a function?[1]
When writing a division on one line, does an implied multiplication bind more tightly than an explicit one?[2]
Is \(a/bc\) equivalent to \(\frac{a}{bc}\) or \(\frac{a}{b}c\)?
There seems to be an unwritten rule "juxtaposition is stickier".
But that might not apply when there are numbers involved: almost everyone would interpret \(2/3x\) as \(\frac{2}{3}x\) instead of \(\frac{2}{3x}\)
The "juxtaposition is stickier" rule only seems to break ties, not override the normal order of operations:
\[ ab^2 = a \times (b^2) \]
Sometimes the ambiguity comes from mistaking a function for an operation:
\[ (a+b) \Phi (a+b)\]
which can be viewed as either \( (a+b)\cdot \Phi(a+b)\), or \(\Phi\) as binary addition-like operation, similar to \( (a+b)\oplus (a+b)\).[3]
