Math Is Fun Forum
You are not logged in.
- Topics: Active | Unanswered
#1376 Re: Help Me ! » Algebra problem » 2006-06-12 03:25:48
luca-deltodesco, 25-9 is 16
dont worry i do it all the time:P
oooh yeh 
#1377 Re: Help Me ! » Binomial Expansion Problem » 2006-06-12 03:06:49
for x and x^2
the coeffecients in the expansion will be
andthe bracket thingy being the binomial expansion thingy
so the ceoffecients are
...
...
...
however... (-2)! is undefined... so i dont see how that can be right
#1378 Re: Help Me ! » Algebra problem » 2006-06-08 05:18:40
just substitue the values
N = 7*(5^2 - 3^2) = 7*(25-9) = 7*14 = 91
V = 5*3^2 = 5*9 = 45
#1379 Re: Help Me ! » graphs slid around with subtraction » 2006-06-07 04:13:00
But a circle isn't a graph!
x^2 + y^2 = r^2 can be rewritten y = +/- sqrt{r^2-x^2}
which if you plot with the +/- will give you a circle
(and if you plot complex numbers aswell, you get a verticaly standing circle, and then two horizontal square root patterns)
take the x axis, as x
the y axis as the real part of the circle function
and the z axis as the imaginary part of the circle function
obviously the circle has all z = 0
and the outper parts have all y = 0
#1380 Re: Help Me ! » please help with RADICALS! » 2006-06-06 10:42:00
#1381 Re: Puzzles and Games » Luca's Puzzles (math) » 2006-06-06 06:45:34
2.
given that:
prove that:
3.
given that:
prove that
4.
Given a two vector
prove that a perpendicular two vector to a is:
#1382 Re: This is Cool » Question about Infinity » 2006-06-05 22:16:45
well i think of it this way
∞ - n = ∞, because no matter what n is, ∞ - n is still going to be infinately big
but ∞ - ∞, i think of it as being, ∞ is infinately big, no matter what number you take away from it, its never going to be big enough unless its ∞...
#1383 Re: Dark Discussions at Cafe Infinity » do you procrationate? » 2006-06-05 21:52:14
i always procraastinate, and it gets really annoying sometimes when i leave LOADS of work till the last minute, and end up rushing or not getting it done
in the case that i dont have a deadline, it often means i just give up on it
#1384 Re: This is Cool » The 6th of June, 2006 » 2006-06-05 21:35:03
I doubt God or Satan run by the Georgian calandar, and if they did, we have/had nothing to worry about anyway. The date is the 6/6/2006, 06 is short for 2006 but it's not the date. The guys back in the in the year 6AD on the other hand ...
nah, they didnt need to worry, Satan can only do his dirty work with his son, so well be waiting until 6/6/6666 (i.e 666 and 666)
only 4660 years, 1 month and 1 day to go!
#1385 Re: Help Me ! » Mechanics 1 - Kinematics Problem » 2006-06-05 21:33:08
I got 1.667 for the accelaration.
well, if you multiply that by 2 you get the correct answer for acceleration at A (3.333...)
#1386 Re: This is Cool » The 6th of June, 2006 » 2006-06-05 19:23:58
is this going to be bad luck for me? exams on 666
#1387 Re: Puzzles and Games » Luca's Puzzles (math) » 2006-06-05 03:06:06
I suppose, the contant term -1 is missing in the question. Am I right?
ah yeh, i thought it looked a little strange, ill change in the question
#1388 Re: Help Me ! » Mechanics 1 - Kinematics Problem » 2006-06-04 09:37:12
luca-deltodesco, it appears you do have the correct answer, but I really don't understand your method. I fear you may have used techniques I haven't yet been taught, and hence, I doubt they'll need to be implemented in the exam. However, thanks for your input and well done for getting the correct answer.
Stardust, yep, that's it! I understand that, it's one of those answers you think, how the hell didn't I get that!? Haha. Fantastic! Thank you so much. And no, my M1 exam is on Tuesday!
Do you get an extra day!?
.. well i dont remember any of the formulae, so i worked them out on the spot via integration (the top part), and then just applied it, and them simultaneous equation, anyways... i have my core 1 and 2 exams on tuesday 
#1389 Re: Help Me ! » Mechanics 1 - Kinematics Problem » 2006-06-04 09:03:28
well i havnt started on mechanics yet, but lets see if i can do it;
so in 4 seconds, the car travels 80m, and in 6s seconds, it travels 140m, since its acceleration is uniform, its velocity is linear, its displacement quadratic.
. now acceleration. its constant so, a(t) = k
and velocity is linear. taking as the integral, v(t) = kt + q
and distance is quadratic, taking as the integral, d(t) = 1/2kt^2 + qt + r
at t = 0, displacement is 0, so r = 0;
d(t) = 1/2kt^2 + qt
d(4) = 80 = 8k + 4q
d(6) = 140 = 18k + 6q
3.d(4) = 240 = 24k + 12q
2.d(6) = 280 = 36k + 12q
taking them away, 2.d(6)-3.d(4)
40 = 12k
k = 10/3
80 - 80/3 = 4q
q = 40/3
d(t) = (5/3)t^2 + (40/3)t
v(t) = (10/3)t + 40/3
a(t) = 10/3
t = 0, v(0) = 40/3, a(0) = 10/3
(wooh go me!) owned by a 15year old
#1390 Re: Puzzles and Games » 10 is fun! » 2006-06-04 06:31:22
1 + 2 + 3 + 4 = 10
1 point is a point
2 points make a line
3 points make a plane
4 points make a solid10 points makes a ???
4 points makes a space
5 points makes a space spread out through time
6 points makes a space spread out through time, spread out through... ehm.. hypertime
7 points makes a space spread out through time, spread out through hypertime, spread out through... ehm.. loltime
8 points makes a space spread out through time, spread out through hypertime, spread out through loltime, spread out through... ehm.. happiness
9 points makes a space spread out through time, spread out through hypertime, spread out through loltime, spread out through happiness, spread out through... ehm..creation
10 points makes a space spread out through time, spread out through hypertime, spread out through loltime, spread out through happiness, spread out through creation, spread out through... ehm.. god.
#1391 Puzzles and Games » Luca's Puzzles (math) » 2006-06-04 04:28:33
- luca-deltodesco
- Replies: 4
1.
A geometric progression U has first term a, where
, and common ratio r, where , the difference between the fourth and first term is equal to four times the difference between the third and second term:a) show that
,b) show that (r-1) is a factor of . hence factorise.
c) hence find two possible values for the common ratio, giving youre answers in exact form
d) for the value of r for which the progression is convergenet prove that
#1392 Re: Jokes » Barber Shop » 2006-06-03 09:42:19
haha, nice one
#1393 Re: Help Me ! » ... equation ... » 2006-06-01 09:32:25
Sure.
yeh i realised that about 20 minutes after i posted it, but the thread seemed to have came to an end, so i didnt change it
#1394 Re: Help Me ! » ... equation ... » 2006-05-31 23:20:33
But if x=0 is a solution, the original question is invalid!
only if you dont like infinity
but really, i think you can say x = 0 is a solution.
as x approaches 0, the value of 4/x and 3/x both approach infinity, and become infintisamely different
#1395 Re: Help Me ! » Permutation » 2006-05-31 19:50:50
edit : the 100! is actually 100 factorial. The ! wasnt the ending of the question heh.. it kinda mislead people.
in which case i have no idea
#1396 Re: Help Me ! » Permutation » 2006-05-31 19:25:09
what do you mean by overflow?
#1397 Re: Help Me ! » Permutation » 2006-05-31 19:23:01
i think it means, so that 10^k will divide into 100, leaving an integer. but i dont know (in which case it would be 2, 100/10^2 = 1)
#1398 Re: Help Me ! » Solving an equation? » 2006-05-31 09:01:38
If i'm told that 0 = -2sin(0.5x) + cos(0.5x) , how would i go about finding x in this situation? Is this called a trigonometric equation, i'm not sure?
Thanks.
well i would solve it this way
tangent repeats every 180degrees, so if you wanted the possible values of x between -360 and 360 degrees, we would have
x = 53.13010235...
x = -306.8698976...
which if you plug back into original equation, equals 0
#1399 Maths Is Fun - Suggestions and Comments » posting your own puzzles like that in ganesh's puzzle page? » 2006-05-28 17:45:19
- luca-deltodesco
- Replies: 1
Is there anywhere were someone, me, can post their own puzzles and questions, not because you cant solve them, but to see if other people can, basicly all the kind of stuff in ganesh' puzzles forum
#1400 Re: Help Me ! » How do you find X? » 2006-05-28 17:33:51
so using logarithms, we also get rearranged
and ofcouse neither this or the root one is a formula for x, since it cant be calculated with just being given n