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Mathematics 20 Online
pooja195 (pooja195):

@mathmate

pooja195 (pooja195):

@mathmate

pooja195 (pooja195):

@Nnesha its not spam ;)

pooja195 (pooja195):

@Nnesha its not spam ;)

OpenStudy (mathmate):

Yes!

OpenStudy (mathmate):

What's your question?

pooja195 (pooja195):

O_o question? XD 2+2=?

OpenStudy (mathmate):

Not allowed to give direct answers. Check the drawing: |dw:1433043776037:dw|

pooja195 (pooja195):

4 LOL

pooja195 (pooja195):

@mathmate ;-;

OpenStudy (mathmate):

That means: 1. i dont like this and 2. i dont understand this OR 3. i dont want to do this Which one/ones?

pooja195 (pooja195):

3 +_+

OpenStudy (mathmate):

gimme a minute!

OpenStudy (mathmate):

Calculate \(\large \frac{1}{2}+\frac{2}{3}\). Show work.

pooja195 (pooja195):

7/6

OpenStudy (mathmate):

Calculate 12+23. \(\huge \color{red}{Show work.}\)

pooja195 (pooja195):

Why are we doing this? .-.

OpenStudy (mathmate):

Because it is the same way you do this as with rational fractions. This is a pretest!

pooja195 (pooja195):

\[12+23=35\]

pooja195 (pooja195):

idk how to show work for that .-.

pooja195 (pooja195):

2+1=3 3+2=5

OpenStudy (mathmate):

ok, that's how it works: Calculate \(\large \frac{1}{2}+\frac{2}{3}\), show work.

OpenStudy (mathmate):

\(\large \frac{1}{2}+\frac{2}{3}=\frac{1*3}{2*3}+\frac{2*2}{3*2}\)

OpenStudy (mathmate):

Do you know why we multiply the first fraction by three, and the second by two?

pooja195 (pooja195):

to get a common denominator

OpenStudy (mathmate):

Exactly!

OpenStudy (mathmate):

Just a review of terms: 1/2 = 2/4 because they are __________________

pooja195 (pooja195):

equivalent

OpenStudy (mathmate):

exactly "equivalent fractions"! That's a good start! You know your stuff.

pooja195 (pooja195):

:)

OpenStudy (mathmate):

The idea of adding and subtracting rational fraction is exactly the same!

OpenStudy (mathmate):

We multiply top and bottom of each term by a factor so that the denominator becomes the common denominator.

OpenStudy (mathmate):

Since each term remains an equivalent fraction, the answer will not change, BUT...

OpenStudy (mathmate):

we now only have to add the numerators of the equivalent fractions, just like the numerical example.

OpenStudy (mathmate):

\(\large \frac{1}{2}+\frac{2}{3}=\frac{1*3}{2*3}+\frac{2*2}{3*2}=\frac{3}{6}+\frac{4}{6}=\frac{7}{6}\)

OpenStudy (mathmate):

Sorry it took a while!

pooja195 (pooja195):

this looks easy :)

OpenStudy (mathmate):

The next one will be equally easy! gimme a minute.

OpenStudy (mathmate):

Calculate \(\large \frac{1}{x}+\frac{2}{x^2}\) show work!

pooja195 (pooja195):

\[\huge~\frac{ 1*x }{ x*x }+\frac{ 2 }{ x^2}=\frac{ 1x+2 }{ x^2 }\]

OpenStudy (mathmate):

Excellent! Just remember that 1x is usually written as x, except when showing work.

OpenStudy (mathmate):

Now: Calculate \(\large \frac{2}{(x-1)}-\frac{1}{(x-1)^2}\) show work!

pooja195 (pooja195):

\[\frac{ 2*(x-1) }{ (x-1)*(x-1) }-\frac{ 1 }{ (x-1)^2 }=\frac{ 1(x-1) }{ (x-1) }=1\]

OpenStudy (mathmate):

The denominator is still meant to be (x-1)^2 ? You need to do the math on the numerators. Give it another shot!

OpenStudy (mathmate):

T_T not allowed!

pooja195 (pooja195):

;-;

pooja195 (pooja195):

i dont get it

OpenStudy (mathmate):

Good! I'll explain!

OpenStudy (mathmate):

\(\large \frac{ 2*(x-1) }{ (x-1)*(x-1) }-\frac{ 1 }{ (x-1)^2 }\) is perfect!

OpenStudy (mathmate):

At this point, both denominators are identical, so we can do the math just on the numerators \(\large \frac{ 2*(x-1) -1 }{ (x-1)^2 }\)

OpenStudy (mathmate):

following so far?

pooja195 (pooja195):

yes

OpenStudy (mathmate):

Now can you do the math (on the numerator) and finish?

pooja195 (pooja195):

\[\frac{ x(x-1) }{ (x-1)^2 }\]

OpenStudy (mathmate):

You need to distribute the first term, and add like terms, 2*(x-1)-1 = 2x-2 -1 =2x-3

OpenStudy (mathmate):

following?

pooja195 (pooja195):

Yes

OpenStudy (mathmate):

So the final answer is....

pooja195 (pooja195):

\[\huge\frac{ x(x-1) }{ 2x-3 }\]

pooja195 (pooja195):

>_<

pooja195 (pooja195):

wrong spot...

pooja195 (pooja195):

\[\frac{ 2x-3 }{ (x-1)^2 }\]

OpenStudy (mathmate):

Whew! Yes, excellent!

OpenStudy (mathmate):

One thing we did without saying it is...nothing. We did "nothing" to factorize the numerator, because it was "obvious" there are no factors.

OpenStudy (mathmate):

In general, after the arithmetic on the numerator, we need to factor the numerator, can you tell me why?

pooja195 (pooja195):

:/ so its easier to multiply or is it to break down the numbers? :/

OpenStudy (mathmate):

So that we can cancel (with condition) IF there are common factors between the numerator and denominator, just like what we did before in the simplification. Does that make sense?

pooja195 (pooja195):

yes

OpenStudy (mathmate):

Are there any points to clarify, or are we good?

pooja195 (pooja195):

We're good.

OpenStudy (mathmate):

ok, now, try this: Calculate \(\large \frac{3}{x}-\frac{2}{x-1}\) show work!

pooja195 (pooja195):

ummm O_O

OpenStudy (mathmate):

Look at the denominators.

OpenStudy (mathmate):

there are no common factors! So you just "cross multiply", which is a short cut when there are no common factors. like \(\large \frac{1}{2}+\frac{3}{5}= \frac{1*5}{2*5}+\frac{2*3}{x*5}=\frac{1*5+2*3}{2*5}=\frac{11}{10}\)

OpenStudy (mathmate):

* 2*5 in denominator

pooja195 (pooja195):

O_o

pooja195 (pooja195):

i thought u can only do that if there is an equal sighn :/

OpenStudy (mathmate):

It's not a real cross multiplication, but it works in a similar way.

OpenStudy (mathmate):

The pattern helps when there are no common factors. You can use that in the new problem.

OpenStudy (mathmate):

Calculate \(\large \frac{3}{x}-\frac{2}{x-1}\), show work! Remember that when there is no common factors in the denominators, the common denominator is just the product, namely x(x-1)

pooja195 (pooja195):

:?

OpenStudy (mathmate):

\(\large \frac{3}{x}-\frac{2}{x-1}=\frac{3(x-1)}{x(x-1)}-\frac{2x}{(x-1)x}=\frac{3(x-1)-2x}{x(x-1)}\)

pooja195 (pooja195):

hmm ok makes a bit more sense

OpenStudy (mathmate):

Good! you can finish it?

pooja195 (pooja195):

\[\frac{ x-1 }{ x(x-1) }\]

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