# Thread: Expressions containing fractions and simplifying

1. ## Expressions containing fractions and simplifying

I have an expression;

(1 - u)(2u + 1/3) I am asked to multiply out the brackets and simplify. I am concerned about the fraction because I cannot find any examples in my course book to help with this type of expression.

am I doing it correctly by this method;

(1 - u)(2u + 1/3) = 2u + 3 - 2u^2 - 3u

Thanks

David

2. ## Re: Expressions containing fractions and simplifying

Nearly.

$4\times{\frac{1}{3}}=\frac{4}{3}$

Just multiply the value by the numerator of the fraction.

So what would:

$-u\times\frac{1}{3}$ be?

Just FOIL it out as you normally would.

3. ## Re: Expressions containing fractions and simplifying

Originally Posted by Quacky
Nearly.

$4\times{\frac{1}{3}}=\frac{4}{3}$

Just multiply the value by the numerator of the fraction.

So what would:

$-u\times\frac{1}{3}$ be?

Just FOIL it out as you normally would.
- u Yes

4. ## Re: Expressions containing fractions and simplifying

I'm confused by your response. Do you understand where you were going wrong?

5. ## Re: Expressions containing fractions and simplifying

Originally Posted by Quacky
I'm confused by your response. Do you understand where you were going wrong?
I will have to look up FOIL to remember it, but please advise if I misunderstood.

- u x 1/3 = - u / 3

No?

6. ## Re: Expressions containing fractions and simplifying

That's right. FOIL is a general approach to quadratics; multiply the:
First,
Outside,
Inside
Last

...terms together. You don't have to use it to expand if you prefer not to. The method you used in the original post is fine except for a very minor error when taking the fraction into account.

7. ## Re: Expressions containing fractions and simplifying

Originally Posted by Quacky
That's right. FOIL is a general approach to quadratics; multiply the:
First,
Outside,
Inside
Last

...terms together. You don't have to use it to expand if you prefer not to. The method you used in the original post is fine except for a very minor error when taking the fraction into account.
So I made TWO mistakes then?

Expression;

(1 - u)(2u + 1/3) = 2u + 1 - 2u^2 - u/3

Thank you

David

8. ## Re: Expressions containing fractions and simplifying

Originally Posted by David Green
So I made TWO mistakes then?

Expression;

(1 - u)(2u + 1/3) = 2u + 1 - 2u^2 - u/3

Thank you

David
The value marked in red is unfortunately wrong because $1 \cdot \frac13 = \frac13$.