Use of BOMDAS in 3rd level?

PoleStar

Hi

I am doing revision on my own prior to starting the OU maths/stats program.

Interestingly, it doesnt use the BOMDAS ordering and uses left to right but also stating that brackets should always be used to avoid confusion.

Is that the norm?

bnt

Um ... do you want to give an example? BOMDAS is pretty much universal, and not something that gets used in one course and not in another. Brackets override BOMDAS of course, that's what they do, but I'll be very surprised if BOMDAS is not being followed, even if only implicitly. If you ever use any Excel, or Stats software such as R or MATLAB, it will be all BOMDAS all the time.

TheBody

PoleStar wrote: »

Hi

I am doing revision on my own prior to starting the OU maths/stats program.

Interestingly, it doesnt use the BOMDAS ordering and uses left to right but also stating that brackets should always be used to avoid confusion.

Is that the norm?

I think you must be getting confused with something. The laws of maths don't change!!

PoleStar

I am not getting it confused!

I am going by their revision book Countdown to Mathematics.

Although maybe it IS too long since I have done mathematics.

Ok, to give an example, simplify the following expression:

9+x+y÷(3x×4y)

Michael Collins

That's fairly unambiguous:

[latex] \displaystyle 9+x+y \div (3x\times4y) = 9+x+\frac{y}{(3x)(4y)}=9+x+\frac{1}{12x}[/latex]

PoleStar

Thats what I would have remembered from my school days.

However the book gives the answer essentially as (sorry I don't know how to do those maths diagrams)

(9+x+y)÷(3x+4y) if you get me and not the way you have done it which is (9+x)+[y÷(3x+4y)].

Thus I am confused. And btw, this wasn't just a typo in the book.

BTW, how DO you do those actually maths diagrams that you put in.

TheBody

PoleStar wrote: »

Thats what I would have remembered from my school days.

However the book gives the answer essentially as (sorry I don't know how to do those maths diagrams)

(9+x+y)÷(3x+4y) if you get me and not the way you have done it which is (9+x)+[y÷(3x+4y)].

Thus I am confused. And btw, this wasn't just a typo in the book.

BTW, how DO you do those actually maths diagrams that you put in.

Brackets are very important.
[LATEX](9+x+y)\div(3x+4y)[/LATEX] is totally different from
[LATEX]9+x+y\div(3x+4y)[/LATEX].

One thing I can assure you is that the laws of maths don't change!! Provided the problem is phrased as you posted above, what Michael Collins did is spot on.

To answer your question about displaying the maths. You need to used Latex tags. Of course this requires you to know some latex code!!

PoleStar

So the book is wrong.

I assume therefore that it is a revision book and perhaps they are trying to keep things simple. I had put the answer that Collins did but when I checked it I was wrong.

I feel reassured now!

So how do I find out about latex codes etc and how to use it here on boards for future reference?

henbane

[thread=2055679780]LaTeX thread here[/thread]

TheBody

There is tons of stuff on Latex here:

http://www.boards.ie/vbulletin/forumdisplay.php?f=1286

Latex code takes some time to learn. People who write maths all the time use Latex. It's free to download if you want to learn it. It takes some time to pick it up. Once you get used to it, you will NEVER go back to using an equation editor like the one with microsoft word.

sponsoredwalk

I'd suggest you learn all you can about 'the field axioms':

https://www.youtube.com/watch?v=5OzmFxJNkbI

These will make even more sense if you learn about functions as
mappings between sets dependent on arity. Basically just find out
about what it means for addition & mutiplication to be thought of as
'binary operations'.

Going by all of this you can think of (9 + x + y)÷(3x + 4y) as

[latex]((9 \ + \ x) \ + \ y) \ \cdot \ (3x + 4y)^{-1}[/latex]

or

[latex](9 \ + \ x) \ + \ (y \ \cdot \ (3x + 4y)^{-1})[/latex]

(or a few other variations)

Once you learn about mappings as binary (ternary, n-ary) operations
you'll really appreciate the fundamental importance of brackets. Also
I'd say if you ever want to do any serious stats you'll need the measure
theory underlying the probability underlying the stats for which all of
this would be helpful.

As for latex, you can use any of these:

α β γ δ ε ζ η θ λ μ ξ ρ Σ σ φ ψ ω Π ∂ Δ Ө Φ x € ∩ ∊ ∪ ⊂ ⊆ ⊃ ⊇ π ¬ ∠ ∡ ∼
₀ ₁ ₂ ₃ ₄ ₅ ₆ ₇ ₈ ₉ ₊ ₋ ₌ ₍ ₎ ⁰ ° ¹ ² ³ ⁴ ⁵ ⁶ ⁷ ⁸ ⁹ - ⁺ ⁻ ⁼ ⁽ ⁾ ª ⁿ ½ ⅓ ⅔ ¼ ¾ ⅛ ⅜ ⅝ ⅞
∫ℯˣ ∮ ∂ ±÷ × • · ≡ ≠ ≅ ≈ ≤ ≥ √ ∑ᵢ ← ↑↔ ↓ → ↦ ⇒ ⇔ θ ∀ ☺ ⊕ ⊗ ⊥ ∞ ∝
Δ ∇ ∀ ∃ ∋ ∈ ∉ ℒ{႒(t)} = ♥ ◊ ♠ ♣ ♦ ∴ ∅ ℕ ℤ ℙ ℚ ℝ ℂ ℵ ℘ ℑ ℜ ¯ ⋀ ⋁ ಠ _ಠ

when it's convenient or else learn just the basic latex commands:

\frac{a}{b} gives a fraction. \cdot gives a multiplication dot. \times gives
a multiplication x sign. To make a space between things just put a \ in.
To get 3⁻¹² write 3^{-12}, to get 3² write 3^2, to get 3₂ ₃ write 3_{2 \ 3}.
So try 1 \ \cdot \ \frac{a}{b}

Put them inside these: [latex] [latex] where the second [latex] is written
as /latex.

So

[latex] (1 \ \cdot \frac{a}{b}) \times (\frac{a}{a}) \ = \ (1 \ \cdot \ \frac{a}{b}) \times((a)\cdot(a^{-1})) = \frac{a}{b} [latex]
[latex] (1 \ \cdot \frac{a}{b}) \times (\frac{a}{a}) \ = \ (1 \ \cdot \ \frac{a}{b}) \times((a)\cdot(a^{-1})) = \frac{a}{b} [ /latex]
[latex] (1 \ \cdot \frac{a}{b}) \times (\frac{a}{a}) \ = \ (1 \ \cdot \ \frac{a}{b}) \times((a)\cdot(a^{-1})) = \frac{a}{b} [/latex]

QuiteInterestin

Hi OP, I'm starting MST 121 in the coming weeks as well. I didn't bother get the Countdown to Mathematics books, I'm just using my old JC/LC maths books and the revision pack the Open University sent us out. Anyways, in the OU revision pack (page 30) it sums up order of operations as BIDMAS:
- Brackets
- Indices
- Division and Multiplication (the order does not matter)
- Addition and Subtraction (the order does not matter)

so whatever about the Countdown to Mathematics book, the Open University notes are definitely in keeping with the laws of maths.

Hope the revision is going well for you.

To the other replies, thanks for the links to Latex, must have a go at it!

PoleStar

QuiteInterestin wrote: »

Hi OP, I'm starting MST 121 in the coming weeks as well. I didn't bother get the Countdown to Mathematics books, I'm just using my old JC/LC maths books and the revision pack the Open University sent us out. Anyways, in the OU revision pack (page 30) it sums up order of operations as BIDMAS:
- Brackets
- Indices
- Division and Multiplication (the order does not matter)
- Addition and Subtraction (the order does not matter)

so whatever about the Countdown to Mathematics book, the Open University notes are definitely in keeping with the laws of maths.

Hope the revision is going well for you.

To the other replies, thanks for the links to Latex, must have a go at it!

That's reassuring! Since I did LC in 1994, my books have long decomposed at this stage so wanted some basic intro! I get the feeling then that the book is just trying to avoid overwhelming readers from a variety of backgrounds and thus has just omitted this.

Revision is going ok. Almost finished the first book and gonna do the second then onto the revision pack. A lot to do therefore in the next couple of weeks!