#1
Yeah, I'm retarded and I don't get functions.

The question is: Find an equation for the family of linear functions such that f (2)=1 and sketch several members of the family.


Anyone good with functions and can help me out?


Note: No one in my dorm has Calculus and the girl in my class has no idea either.
Quote by SteveHouse
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#3
Uh...I do not know what you are talking about
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M. Night Shyamallama

#6
Find an equation for the family? I don't understand the question, there are a fair few functions that would satisfy f(2)=1, some of them unrelated.
#7
there are an infinite amount of equations that would satify f(2)=1.
i.e - f(x)= 2x-3; f(x)=5x-9; f(x)=20x-39. and so forth. your ultimate goal is that you have to substitute 2 for x in any equation and your final answer has to equal 1. meaning that after you substitute 2 for x, you can multiiply, divid, add or subtract any way you want. it just as to be in an equation.
im stupid. blahbalhblahblah
#10
Quote by National_Anthem
Ah, I get it.
I think the expression that satisfies f(x)=1 is nx - 2n-1


If you going that way it should have been f(x) = nx - (2n-1). But what about division? f(x)=x/2 would satisfy f(2)=1.
#11
Quote by MakeItY0urs
there are an infinite amount of equations that would satify f(2)=1.
i.e - f(x)= 2x-3; f(x)=5x-9; f(x)=20x-39. and so forth. your ultimate goal is that you have to substitute 2 for x in any equation and your final answer has to equal 1. meaning that after you substitute 2 for x, you can multiiply, divid, add or subtract any way you want. it just as to be in an equation.


This.
Quote by denizenz
I'll logic you right in the thyroid.

Art & Lutherie
#12
Quote by rjdusa
If you going that way it should have been f(x) = nx - (2n-1). But what about division? f(x)=x/2 would satisfy f(2)=1.


What I posted is exactly the same as what you posted, only I wrote it as an expression, you wrote it as a function. f(x)=x/2 is not a linear function.
#13
Quote by National_Anthem
What I posted is exactly the same as what you posted, only I wrote it as an expression, you wrote it as a function. f(x)=x/2 is not a linear function.


f(x) = x/2 is a linear function.
Quote by denizenz
I'll logic you right in the thyroid.

Art & Lutherie
#15
Dayam I'm starting a maths degree in like 4 weeks and I well have to think about this.
Drank too much this summer.

Makeityours is right but if you have to find an equation for the whole family, here goes:
f(x)=ax-(2a-1)

Try that
#16
Quote by adyhendrixc
Dayam I'm starting a maths degree in like 4 weeks and I well have to think about this.
Drank too much this summer.

Makeityours is right but if you have to find an equation for the whole family, here goes:
f(x)=ax-(2a-1)

Try that

I already said that. Don't think you're getting the credit
#17
I hope TS doesn't mind but I have a math question myself and it's a pretty simple one, I'm just a stupid person.

So I am doing the quadratic formula and I can solve it most of the time when the square root part of the formula is a perfect square. When it is NOT a perfect square I just go braindead and have no idea what to do.

Here's an example http://www.purplemath.com/modules/quadform.htm
It's the second problem on that site, and although it shows step by step how to do it, I have no idea what they did.
#18
Quote by National_Anthem
What I posted is exactly the same as what you posted, only I wrote it as an expression, you wrote it as a function. f(x)=x/2 is not a linear function.

Actually in your case if n was 20, it would be 40x - 41, his would be 40x - 39.
2 ducks and a rabbi walk into a bar.
The rabbi enjoys a nice drink and the ducks are shooed out so that health services aren't called in.
The day proceeds as normal.
#19
Quote by National_Anthem
I already said that. Don't think you're getting the credit


So you did haha I just wrecked by brain needlessly for that
#20
Quote by National_Anthem
What I posted is exactly the same as what you posted, only I wrote it as an expression, you wrote it as a function. f(x)=x/2 is not a linear function.


The difference I was going for was the parenthesis, not the function.

EDIT: Sorry if it seemed like I was trying to steal the credit.. just trying to make it more precise.
Last edited by rjdusa at Aug 28, 2008,
#21
2x^2 – 4x – 3 = 0

To solve using the quadratic formula, you set up your equation in the form of ax^2 + bx + c = 0.

Here, a = 2, b = -4, and c = -3.

You know that the roots of a quadratic equation are x = ( -b +/- sqrt(b^2 - 4ac) ) / (2a)

Plug in the values for a, b, and c and solve. If you can't plug it in properly, boo-hoo.
Quote by denizenz
I'll logic you right in the thyroid.

Art & Lutherie
#22
Quote by Masamune
I hope TS doesn't mind but I have a math question myself and it's a pretty simple one, I'm just a stupid person.

So I am doing the quadratic formula and I can solve it most of the time when the square root part of the formula is a perfect square. When it is NOT a perfect square I just go braindead and have no idea what to do.

Here's an example http://www.purplemath.com/modules/quadform.htm
It's the second problem on that site, and although it shows step by step how to do it, I have no idea what they did.

What they've done is used surds. Root n is the same as root (one factor of n) multiplied by root (another factor of n) as long as both factors of n multiply to make n.
Therefore, root 40 = root 4 * root 10
Root 4 is 2
So it's 2*root 10 or simply 2 root 10
They've then factorised 4 +- 2 root 10 by dividing by 2, to get 2(2+-root10)
They've also factorised the four on the bottom to get 2(2)
the 2s cancel out so you are left with (2+-root10) / 2
2 ducks and a rabbi walk into a bar.
The rabbi enjoys a nice drink and the ducks are shooed out so that health services aren't called in.
The day proceeds as normal.
#23
Quote by Masamune
I hope TS doesn't mind but I have a math question myself and it's a pretty simple one, I'm just a stupid person.

So I am doing the quadratic formula and I can solve it most of the time when the square root part of the formula is a perfect square. When it is NOT a perfect square I just go braindead and have no idea what to do.

Here's an example http://www.purplemath.com/modules/quadform.htm
It's the second problem on that site, and although it shows step by step how to do it, I have no idea what they did.


Try solving those by completing the square rather than using the quadratic formula. It's essentially the same thing, I just find it can make it a bit simpler when the numbers get a little awkward.
Example, in case you don't already know:
Solve
y=x^2 + 4x + 2 = 0

x^2 + 4x = -2
(x+2)^2 - 4 = -2
(x+2)^2 = 2
x + 2 = +/- sqr root 2
x = -2 +/- sqr root 2
#24
Quote by Masamune
I hope TS doesn't mind but I have a math question myself and it's a pretty simple one, I'm just a stupid person.

So I am doing the quadratic formula and I can solve it most of the time when the square root part of the formula is a perfect square. When it is NOT a perfect square I just go braindead and have no idea what to do.

Here's an example http://www.purplemath.com/modules/quadform.htm
It's the second problem on that site, and although it shows step by step how to do it, I have no idea what they did.


If you haven't learnt surds it would be extremely difficulty to understand
I'm using/ as square root here
from /40 they've taken it to /10/4
/10 x /4 = /40
and /4 = 2

Then they've divided everything on top by 2

Hope that helps if I'm looking at the right problem and that's the bit you're stuck with
#27
Quote by National_Anthem
Try solving those by completing the square rather than using the quadratic formula. It's essentially the same thing, I just find it can make it a bit simpler when the numbers get a little awkward.
Example, in case you don't already know:
Solve
y=x^2 + 4x + 2 = 0

x^2 + 4x = -2
(x+2)^2 - 4 = -2
(x+2)^2 = 2
x + 2 = +/- sqr root 2
x = -2 +/- sqr root 2


Beat me to it again
Even though you have a different method to me.
Completing the square confuses me I've not done it in a while.
Anyways at least I'm getting some practise before uni and I dont look like a complete thick ****
#28
Quote by Masamune
Alright thank you guys

Any time
2 ducks and a rabbi walk into a bar.
The rabbi enjoys a nice drink and the ducks are shooed out so that health services aren't called in.
The day proceeds as normal.
#29
Quote by rjdusa
The difference I was going for was the parenthesis, not the function.

EDIT: Sorry if it seemed like I was trying to steal the credit.. just trying to make it more precise.

I'm really not bothered about the credit, I was only joking, hence the

Quote by Magic Jim
Actually in your case if n was 20, it would be 40x - 41, his would be 40x - 39.


I apologise for any errors I'm making, as said I'm braindead tonight. As the other guy said, put the bracket there and it's sorted.

Quote by adyhendrixc
Beat me to it again
Even though you have a different method to me.
Completing the square confuses me I've not done it in a while.
Anyways at least I'm getting some practise before uni and I dont look like a complete thick ****


How do you do it? I'd be interested to find out.