Mathematics - 21 October 2007

Scientist can determine the age of ancient objects by a method called radiocarbon dating. The bombardment of the upper atmosphere by cosmic rays converts nitrogen to a radioactive isotope of carbon, 14C, with a half-life of about 5730 years. Vegetation absorbs carbon dioxide through the atmosphere and animal life assimilates 14C through food chains. When a plant or animal dies, it stops replacing its carbon and the amount of 14C begins to decrease through radioactive decay. Therefore, the level of radioactivity must also decay exponentially. A parchment fragment was discovered that had about 78% as much 14C radioactivity as does plant material on Earth today. Estimate the age of the parchment.

No idea where to start on this one?

2007-10-21 12:59:27 · 5 answers · asked by m_carl 1

The problem is "The height (y) of Marla's model rocket can be represented by the equation y = -16x^2 + 70x + 37 where(x) represents the time in seconds since the rocket was launched, and height is expressed in feet. What was the maximum height of Marla's rocket to the nearest tenth of a foot?" I've got a lot of questions like that one and I have no idea how to answer them. Please help.

2007-10-21 12:52:17 · 3 answers · asked by Anonymous

Josh and Mike live 13 miles apart. Yesterday Josh started to ride his bike towards mikes house. a little later mike started to ride his bike toward joshs house. when they met josh had ridden for twice the time as mike and at 4/5 mikes rate. How many miles had mike ridden when they met?

2007-10-21 12:50:26 · 1 answers · asked by ~USA~ 2

2007-10-21 12:50:23 · 1 answers · asked by Anonymous

how do you find the coordinates of the foci of an ellipse?

also

how do you write the equation of an ellipse

and parabola?

2007-10-21 12:40:49 · 1 answers · asked by nativebeauty22 1

i know how to find it..justu that i am not getting the right answer!!!!!

2007-10-21 12:31:24 · 2 answers · asked by Riya A 1

The Reflector on a bicycle wheel is 15cm from the rim. The diameter of the wheel is 76cm at time = 1/2 sec, the reflector is at its lowest point; 3/4 sec later it returns to the same position.Find an equation which will locate the height of the reflector above the ground at any time t.

a) Find height when t=5.2 sec
b) Find the 1st time the reflector is at a height of 59cm above the ground

Can u help me find the equation i have one but i dont know if its correct

Equation- y = -23 Cos [ 2pi/.75(x-.5)]+38
can u comfirm this? plz so i can calculate a & b

2007-10-21 12:25:45 · 1 answers · asked by Kruschiv 1

The function f(x) = 72,900/100x^2+729 models the percentage of people in the United States who are unemployed as a function of years of education, x.

Find and interpret f(0)
Find and interpret f(20)
Is there an educational level that leads to guaranteed employment? If not, how is this indicated by the equation of the horizontal asymptote associated with this function?

PLEASE ONLY ANSWER IF YOU ARE CONFIDENT IN YOUR RESPONSE THANX!!

2007-10-21 12:25:07 · 1 answers · asked by diamondintheruff 2

Please help me solve for y

2007-10-21 12:21:41 · 1 answers · asked by Paul G 1

2007-10-21 12:18:04 · 3 answers · asked by amani h 1

2007-10-21 12:16:57 · 7 answers · asked by amani h 1

Show that fxx + fyy + fzz = 0 when w= f(r,theta,z) = ln(r) +3z

I thought I could just take the second derivs based on r,theta,z, but that doesnt work out. So im guessing I need to convert into x,y,z, but I can't figure out how to do that.

Help is appreciated. Always give best answer.

2007-10-21 12:15:33 · 1 answers · asked by James B 3

Apologies if this is a really simple question (I think it is :P)

1 / ( 4 - sqrt(8) )

Give this in the form a + b*sqrt(2).

2007-10-21 12:09:23 · 1 answers · asked by Mark 2

1/2 + 2/3 x 1/3

1/9 + 3/8 (divided by) 9/4

9/14 - 1/2 x 1/2

13/16 - 25/18 (divided by) 10/3

2007-10-21 12:08:22 · 6 answers · asked by Anonymous

Can someone give me an explanation on how to solve it plus the answer? There are many more q's like it so I am not really cheating...

the height of a cube is 2x cm, the width is x cm and the length is (x + 1) cm
Find the value of x, to two decimal places for which the cuboid has a volume of 8 cm 3 (cubed)

2007-10-21 12:07:03 · 3 answers · asked by browncow 1

The simplest arithmatic method is quadratic formula; correct?

I'm not looking for the answer; I just want to be clear that there is not an easier arithmatic method. Thanks

2007-10-21 11:59:10 · 3 answers · asked by RogerDodger 1

PLEASE HELP!

2007-10-21 11:51:18 · 7 answers · asked by Anonymous

2007-10-21 11:38:32 · 11 answers · asked by SASSY 1

Is there any way to solve the 1/x ∫ x^2 sin (4.156/x) dx without using a calculator? I think you can pull out the x^2 from the integral to make it x ∫ sin(4.156/x) but I don't know how to go from there. Help is greatly appreciated.

2007-10-21 11:35:48 · 2 answers · asked by Satrivaini 1

2007-10-21 11:35:31 · 1 answers · asked by Anonymous

find the second order derivative and evaluate at x=3

y = 10x^3 + 8x^2 + 19

f(x) = (4x - 1)(3x^2 + 2)

find the successive derivatives and evaluate at x=2

f(x) = 2x^3 + 7x^2 + 9x - 2

f(x) = (8 - 2x)^4

please help me with that lol:) ..id really, really appreciate it :)

2007-10-21 11:35:13 · 1 answers · asked by Mathema-what?! 1

The question is:
What is the minimum number of people you need, so that if you randomly select any two people from that group, there is a 50% chance that their birth dates will be the same?!!

2007-10-21 11:30:39 · 2 answers · asked by shish_101 3

2007-10-21 11:30:04 · 2 answers · asked by Anonymous

2007-10-21 11:25:40 · 5 answers · asked by Anonymous 2

the part where i circled...after the u-substitution and find out what their value is, what do u do next? can u plz guide me how to get those steps...

http://i181.photobucket.com/albums/x85/ctti_3/Untitled-83.jpg

2007-10-21 11:21:54 · 3 answers · asked by pnetecos 1

find the average:

1. 2/3 + 3/5

2. 1/6 + 2/3 + 5/9

3. 11/4 + 5/2 + 7/3

4. 3/4 + 3 + 6/7

2007-10-21 11:21:46 · 10 answers · asked by Anonymous

Only 4% of people have type AB blood.

a. On average, how many donors must be checked to find someone with type AB blood?

b. What is the probability that there is a type of AB blood donor among the first 5 people checked?

c. What is the probability that the first type AB donor will be found among the first 6 people?

d. What is the probability that the first type AB donor will be found on or after the 10th person checked?

e. What is the probability that the first type AB donor will be found on or before the 5th person checked?

2007-10-21 11:18:54 · 2 answers · asked by yohitslindah 1

how do you show that the sum of two concave functions is also concave?

2007-10-21 11:17:48 · 4 answers · asked by Anonymous

2007-10-21 11:15:02 · 5 answers · asked by henry j 1

I can't believe I'm asking this, because I should know this answer but I'm now doubting myself.

If a function goes to infinity as x approaches some real number, would we say the limit as x approaches that number is infinity or would we say that it does not exist?

Doesn't the limit always have to be a real number, but infinity isn't one?

So for example:
the limit as x approaches 0 from the right of 1/x is infinity or not defined?

2007-10-21 11:11:58 · 2 answers · asked by buck r 2