Can someone plz help me get started on these fractions
f(x)=3x-8 div 4x+20

- anonymous

Can someone plz help me get started on these fractions
f(x)=3x-8 div 4x+20

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- anonymous

What do you need?

- saifoo.khan

\[\frac{ 3x - 8}{4x + 20}\to \frac{3x-8}{4(x+5)}\]As there is nothing common between denominator and numerator so we cannot simply it.

- anonymous

sorry I just found this.

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## More answers

- saifoo.khan

No worries! :D

- anonymous

How do I find the domain

- anonymous

hi

- Akshay_Budhkar

domain is all real numbers except for -5

- anonymous

No division by zero. So what is x going to be when the denominator is zero?

- anonymous

0

- saifoo.khan

set the denominator equal to zero right? @Akshay_Budhkar

- anonymous

no. x cannot = -5.

- Akshay_Budhkar

Yes @sai

- Akshay_Budhkar

@saifoo.khan

- anonymous

f(x)=3x-8 over 4x+20

- anonymous

@denise9423 Domain means all of the values x can take on.
Here's your domain:
\[x \neq-5\]

- Akshay_Budhkar

If you have a look the function is having real values for all values except for x=5 when it is not defined as the denominator is zero

- anonymous

can you show me how to get 5

- anonymous

4x+20 =0
Solve for x.
x=-5.

- anonymous

Do you know why division by zero is not allowed?

- anonymous

ok,then can i sub it also 3x-8

- anonymous

no!

- anonymous

you only need to worry about the bottom.

- anonymous

no to ur question
ok

- anonymous

Remember this: What is 1 divided by 0? In other words, what times zero can equal 1? 0*2? 0*3? There is nothing you can multiply by zero to get 1.
So whenever you get these fractions and they ask you to find the domain, just think about what x has to be in order for the denominator to equal zero.

- anonymous

If you have an equation in the denominator, then set that equal to zero :-)

- anonymous

*and solve for x.

- anonymous

like this 4x+20=0

- anonymous

Yup! :-)

- anonymous

ok

- anonymous

Or if you have 1/(x^2+2x+3) . If you have something weird like that, then set it equal to zero and use the quadratic formula to solve for your two x-values. Those x-values are what x can't equal. Sorry, I sound like I'm talking in riddles lol.

- anonymous

ok so -7xyy over 28xxxxxy=0

- anonymous

Are you in algebra?

- anonymous

yes and Its rough

- anonymous

I'm gonna be more specific with what I said, sorry my fault:
Or if you have 1/(x^2+2x+3) . If you have something weird like that, then set it equal to zero and use the quadratic formula to solve for your two x-values. Those x-values are what x can't equal. Sorry, I sound like I'm talking in riddles lol.
x^2+2x+3 = 0 (then use the quadratic formula and solve for x)

- anonymous

That's okay!

- anonymous

I don't think they'll ask you to find the domain of something with x's and y's. Or are they?

- anonymous

yes

- anonymous

no sorry

- anonymous

simplify

- anonymous

I can help you on something like that, but first off is that denominator stuff making sense? Really sleep on that and try to remember it b/c it's super important for calculus.

- anonymous

-7xyy/28xxxxxy

- anonymous

Okay well what multiples to 7 and 8 have in common? What can you divide them both by?

- anonymous

I mean 28.

- anonymous

yes it does bc it will help me remember to put=0 so I can solve for x

- anonymous

good :-)

- anonymous

4

- anonymous

-7xyy/28xxxxxy
You can divide the numerator and denominator by 7.
Also, which has the smallest amount of x's, and then which one has the smallest amount of y's?

- anonymous

3x7=28

- anonymous

no 4x7=28

- anonymous

The numerator has the smallest amount of x's. There is 1 of them. The denominator has the smallest amount of y's, which is 1 y.
So we'll divide the numerator and denominator by 7.
-1*x*y*y/4xxxxxy

- anonymous

bottom has 5 x's and the top has 2 y's

- anonymous

We have to cancel out the smallest amount of x's. And we also cancel out the smallest amount of y's.
So we have: -1*y/4xxxx
I canceled out an x on the top and bottom. Then I canceled out a y on the top and bottom.

- anonymous

ok

- anonymous

sorry i have a 911 gotta chk out b back later thank you for all ur help god bless

- anonymous

k

- anonymous

Anyway, -1*y/4xxxx can be re-written as:
-y/4x^4
See Paul, my favorite math teacher: (I swear by his notes)
http://tutorial.math.lamar.edu/Classes/Alg/IntegerExponents.aspx

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