基本上還是有人堅持所謂的括弧前面的整數是係數要先算或者變數前面係數要先算應該是基於代數上有些學派自己在用的(implicit multiplication rule),但這並不是什公認的規則,只是某學派自己認定,而不像基本的"PEMDAS/BEDMAS"為所有數學家公認的...
代數也是基於PEMDAS/BEDMAS才站的住腳的,若一旦有所衝突,肯定以PEMDAS/BEDMAS為主!所以嚴格來說,6÷2(1+2)=？這種題目是要當成9才是比較正確的.
要當成1,那就是採用implicit multiplication rule學派才會如此...但這不是被所有數學家承認的...
看這十年來計算機大廠漸漸將1/2X當成(1/2)X來看,應是大勢所趨!

再貼一次有專家對這部份說法
History of the Order of Operations:
http://mathforum.org/library/drmath/view/52582.html
5. There is still some development in this area, as we frequently hear
from students and teachers confused by texts that either teach or
imply that implicit multiplication (2x) takes precedence over
explicit multiplication and division (2*x, 2/x) in expressions
such as a/2b, which they would take as a/(2b), contrary to the
generally accepted rules. The idea of adding new rules like this
implies that the conventions are not yet completely stable; the
situation is not all that different from the 1600s


More on Order of Operations:這是一位教授寫信去mathforum問有些派系認為基於某些代數implicit multiplication rule的觀點(記的purplemath有一篇就是此派看法)
http://mathforum.org/library/drmath/view/57021.html
mathforum的回覆:
I ran across the same AMS reference that you found while trying to see
if any societies had made official statements on the rules of
operations in general; the fact that they took note of this one rule
alone demonstrates only that this is the one rule on which there is
not universal agreement at the present time, but it probably is
growing in acceptance.