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## #1 2006-06-15 17:26:23

daniel4544
Guest

### Urgent! Some algebra!

Hey, I have some question on college algebra
1. Is the line y= |x| symetric about the line y=x

2. How do you prove points A(-1,2) B(3,-2) C(-6,-3) are vertices of a right triangle?

3. given f(x)= 2x if 0<x<1, 1-x if 1=<x<2 , 0 if 1=<x=<3: find the domain,f(1), f(2), f(3), and f(0.1).

4. object thrown moves at a height in meters per second is represented With h(t)=20t-4.9t^2: find the height in x seconds, if time increases by 2 how migher is the object, how high does it move per second, if time increased by h how much higher is it?

5. buying 0-5 socks costs 3.50, buying 6-10 socks costs 3.00, buying more than 10 costs 2.75.  Graph the compound function representing cost of buying n socks.

6. In testing an diet for horses, it was found the average weight w was a linear function of days d after the diet started where 0=<d=<300.  determine w as a linear function d and find the average wieght of a horse when d=250

## #2 2006-06-15 19:35:01

luca-deltodesco
Member
Registered: 2006-05-05
Posts: 1,470

### Re: Urgent! Some algebra!

1) yes
2) lots of ways, the quickest way would be to the find the dot product between (b-a) and (c-a), (a-b) and (c-b), (b-c) and (a-c)
(3--1)*(-6--1) + (-2-2)*(-3-2) = 4*-5 + -4*-5 = 0 (right angle) therefore its a right angled triangle

The Beginning Of All Things To End.
The End Of All Things To Come.

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## #3 2006-06-15 20:36:45

MathsIsFun
Registered: 2005-01-21
Posts: 7,659

### Re: Urgent! Some algebra!

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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## #4 2006-06-16 03:21:46

Ricky
Moderator
Registered: 2005-12-04
Posts: 3,791

### Re: Urgent! Some algebra!

1.  I agree with MathIsFun.

3. Domain: (0, 3).  To find f(0), f(1)... etc, just plug in the poitns.

4. This doesn't really make any sense.  Finding the height in x seconds, well, it's already given to you in t seconds.  So just replace the the t with x?  And when you increase the time by 2 seconds, it could do a lot of things.  Depends on where you start.

5.  Is it per sock?  That's the only way the question would ever make sense.  If it is...

The cost of buying 0-5 socks is 3.50x, the cost of buying 6-10 socks is 3.00x and the cost of more than 10 is 2.50x.  Just set up a piecewise function.

"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

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