Algebra, rearranging equations

1. Nov 3, 2009

jamesd2008

Hi hope someone can help explain this for me.

If i have the equation of a=square root of b/b+1 why do can i not cancel the b's? If the equation was square root of bc/bd i can cancel the b's right?

Thanks
James

2. Nov 3, 2009

Staff: Mentor

You can cancel the b's only when they are factors of both the numerator and denominator. b is not a factor of the expression b + 1. Put some numbers in and see how it works. If b = 3, then your expression is 3/(3 + 1) = 3/4. If you (mistakenly) cancelled b, you would get 1/(1 + 1) = 1/2, which is, of course, incorrect.

In your second example, b is a factor of both numerator and denominator, so you can cancel to get c/d.

3. Nov 3, 2009

James

4. Nov 3, 2009

symbolipoint

When someone presents a question like this, the trouble is ignoring of the properties of numbers which the person is expected to learn and use.

What is the justification for either canceling the b's of not canceling the b's?

5. Nov 4, 2009

arildno

OP's expression, "a=square root of b/b+1" is extremely ambiguous:

Which interpretation to choose:
1. $$a=\sqrt{\frac{b}{b}+1}$$ "a=square root of ((b/b)+1)"

2. $$a=\sqrt{\frac{b}{b+1}$$ "a=square root of (b/(b+1))"

3. $$a=\frac{\sqrt{b}}{b}+1$$ "a=((square root of b)/b)+1)"

4. $$a=\frac{\sqrt{b}}{b+1}$$ "a=(square root of b)/(b+1)"

5. $$a=\sqrt{\frac{b}{b}}+1$$ "a=(square root of (b/b))+1"

Last edited: Nov 4, 2009
6. Nov 4, 2009

jamesd2008

Thanks for the reply's it was statement 2 that I was considering in the problem.

7. Nov 4, 2009

Kak-Hazhar

Hi you seem to know LaTeX.

I know this forum supports LaTeX and it's nice, but i want learn LaTeX, so what is your best advice, i.e. what LaTeX programs are good for writing Lab-reports?

another question i've got is, do you write the code for every expression or do you use the forum help with inserting code from menu?
Which one would you recommend?
thanks

8. Nov 5, 2009

arildno

But, do you understand how unclear your question was?