Writing formulas concisely

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Probability

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Would these two examples be clearly wrong!

V = p x r x r x h

Written concisely

hpr^2

Thinking back to BIDMAS I took the r value as squared to be a higher priority, therefore I wrote;

r^2hp

Would this be clearly wrong if marked for an examination say?

Another example to be written in the usual convention;

P = (a + b)^2

Written in the usual convention

P = 2(a+b)

I was thinking along the lines of multiplying out the parenthesis, hence I wrote;

P = (a+b) (a + b)

I take it this would be clearly incorrect?
 
Probability said:
Would these two examples be clearly wrong!

V = p x r x r x h

Written concisely

hpr^2

Thinking back to BIDMAS I took the r value as squared to be a higher priority, therefore I wrote;

r^2hp

Would this be clearly wrong if marked for an examination say?
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Order doesn't matter; multiplication is commutative. So hpr^2 and r^2hp mean exactly the same thing. Why do you think either would be wrong?

In normal typography, they are [MATH]hpr^2[/MATH] and [MATH]r^2hp[/MATH], and there is no ambiguity; in inline form the 2 alone would be properly taken as the exponent, but it would be clearer to write r^2hp as r^(2)hp or r^2 h p.

Probability said:
Another example to be written in the usual convention;

P = (a + b)^2

Written in the usual convention

P = 2(a+b)

I was thinking along the lines of multiplying out the parenthesis, hence I wrote;

P = (a+b) (a + b)

I take it this would be clearly incorrect?
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Are you saying that you think P = (a + b)^2 and P = 2(a+b) mean the same thing? Why? The first is squaring and the second is doubling, which are entirely different.

You could write the former as P = (a + b) (a + b) if you wish, but you would normally do that only if you are then going to use "FOIL" to expand it. Why do you think it would be incorrect (as opposed to merely unsimple)?
 
[MATH]hpr^2 = r^2hp[/MATH]
BIDMAS tells to to square r before doing multiplication regardless of the order in which the variables are written.
 
JeffM said:
[MATH]hpr^2 = r^2hp[/MATH]
BIDMAS tells to to square r before doing multiplication regardless of the order in which the variables are written.
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Squaring IS multiplication.
 
lev888 said:
Squaring IS multiplication.
Also, BIDMAS says nothing about squaring, only multiplication.
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I in BIDMAS stands for indexing, which is frequently used in the UK to mean exponentiation. So BIDMAS does say to deal with exponents first. And yes, integer exponents do mean multiplication, but the rule says to deal with that kind of multiplication first.
 
JeffM said:
I in BIDMAS stands for indexing, which is frequently used in the UK to mean exponentiation. So BIDMAS does say to deal with exponents first. And yes, integer exponents do mean multiplication, but the rule says to deal with that kind of multiplication first.
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I double checked and deleted that part of my post immediately. Should've checked what indices meant.
 
Sorry I made a typo in my first post. P = (a+b)2 is correct and not ^2. The example asked for the formula to be rewritten following the usual convention.

They give one example of what they explain to be usual convention by this example;

d = t x s. They say this is usually written as d = st.

I followed that line of reasoning when I wrote my answer to the first question V = p x r x r x h

I didn't see anything wrong writing r^2hp

The answer given is hpr^2

Getting back to the last example; P = (a+b)2

I thought P = (a+b) (a+b)

The answer given is P = 2(a+b)

It looks like my reasoning was wrong, hence;

P = 2 x a = 2a and

2 x b = 2b, hence P = (2a+2b)

My thought was (a+b) (a+b) = a^2 + ab + ab +b^2) = a^2 + ab^2 + b^2
 
JeffM said:
I in BIDMAS stands for indexing, which is frequently used in the UK to mean exponentiation. So BIDMAS does say to deal with exponents first. And yes, integer exponents do mean multiplication, but the rule says to deal with that kind of multiplication first.
Click to expand...
This is what sometimes throws a lot of confusion in the subject of math's for me. I see many variations others use and can and do become confused at times with it all!!
 
Probability said:
Sorry I made a typo in my first post. P = (a+b)2 is correct and not ^2. The example asked for the formula to be rewritten following the usual convention.

They give one example of what they explain to be usual convention by this example;

d = t x s. They say this is usually written as d = st.

I followed that line of reasoning when I wrote my answer to the first question V = p x r x r x h

I didn't see anything wrong writing r^2hp

The answer given is hpr^2

Getting back to the last example; P = (a+b)2

I thought P = (a+b) (a+b)

The answer given is P = 2(a+b)

It looks like my reasoning was wrong, hence;

P = 2 x a = 2a and

2 x b = 2b, hence P = (2a+2b)

My thought was (a+b) (a+b) = a^2 + ab + ab +b^2) = a^2 + ab^2 + b^2
Click to expand...
There is a convention suggested to students to write a single numeral before letters and to write letters in alphabetical order. It helps prevent mistakes and assists in simplifications. It really does not apply outside of the school room although the rule about numerals is almost always followed. But it is a matter of format, not substance.

[MATH]e = mc^2[/MATH] does not follow that rule, but they gave Einstein the Nobel Prize anyway.
 
lev888 said:
Could you explain your reasoning? How does (a+b)2 become (a+b)(a+b)?
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Because I have literally taken the formula at face value and thought 2 was referring to a+b twice, probably in my minds eye adding ^ to the 2 making it squared.
 
JeffM said:
There is a convention suggested to students to write a single numeral before letters and to write letters in alphabetical order. It helps prevent mistakes and assists in simplifications. It really does not apply outside of the school room although the rule about numerals is almost always followed. But it is a matter of format, not substance.

[MATH]e = mc^2[/MATH] does not follow that rule, but they gave Einstein the Nobel Prize anyway.
Click to expand...
It's all a learning curve for me to keep my mind active. Thanks
 
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