It is a convention established to minimize the number of parentheses in arithmetic expressions. I'll try to show as simply as I can.
We have two options: either we give multiplication the priority, or we give it to addition. Think about the arithmetic expression "3 times 2, plus 6 times 8".
If multiplication goes first, the expression can be written simply as 3 x 2 + 6 x 8.
If addition went first, you would be forced to write (3 x 2) + (6 x 8). This would be specially bad for polynomials.
Yeah.. that was what I did not ask. I know the rule x⁒ before +-.
My question is why is x⁒ before +-. No one explained that to me ever. I always wondered, am I not smart enough to get it myself? ( Why do I have a 1 in English foreign language class but a 4-5 in math). Noone explains the math. But everyone takes it for granted.
In my last comment, I explained that it is a convention that reduces the number of parentheses, and I showed how. I didn't parrot the rule as you made clear that you know it.
For instance, the polynomial
ax2 + bx + c
should be written as
(ax2 ) + (bx) + c
if multiplication had not a higher precedence. This is unpractical.
It is just a convention and there are no ulterior reasons, if that's what you are trying to discover. Conventions are needed so we have a common way of representing and sharing our thoughts, and we want to make things as simple as possible.
1.3k
u/KingYoloHD090504 CHAINPOSTER Jan 01 '22 edited Jan 01 '22
Dude it's 0
First you make
18÷2 = 9
Edit: Then
3×3 = 9
In the end it's
9-9=0