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# P3 Parametrics question. watch

1. (Original post by mathematician)
ok there u have it, thts why we discard 2t-1, becos t>0
Can u write down in steps how it shud be answered cos im still confused.
2. (Original post by lexazver203)
(c) prove that the line l only cuts C at the point B.
For curve C, dy/dx = 2/3t At t=2, dy/dx = 1/3 Rearrange l to y = mx + c, you get y = 2/3*x - 4/3 which is weird as they should have the same gradient showing that l is a tangent to C so will only cross it once. Strange...
3. Its alright Mathsey was doing it weird way we dont get cos he was doing an impossible question.!!!!!!
the data he was given was wrong!
Does anyone actually read the ammendments?
P.S i know my spelling sucks!
4. (Original post by lexazver203)
only thing is that it is +4 not -4
I've multiplied through by -1 so that the t^3 term has a positive coefficient as I prefer to work like this - I didn't make that clear, sorry
5. I'll do the entire questions and hope its all good!

y=t^2 x =t^3

3y-2x+4=0
Sub in values and get

3t^2 - 2t^3 +4 =0
t^2(3-2t)=-4
therofer t =2
Put t in
y = 2^2=4
x= 2^3= 8 Tah dah!!!!!!!!!!!!
Now we have co ordinates so can we let this quezzy go?
6. Only 14 posts after me xyter
7. (Original post by Bezza)
Only 14 posts after me xyter
do u all get it
8. (Original post by XYTER)
I'll do the entire questions and hope its all good!

y=t^2 x =t^3

3y-2x+4=0
Sub in values and get

3t^2 - 2t^3 +4 =0
t^2(3-2t)=-4
therofer t =2
Put t in
y = 2^2=4
x= 2^3= 8 Tah dah!!!!!!!!!!!!
Now we have co ordinates so can we let this quezzy go?

How do you know t=2?
9. Wat u talkin bout Bezza?
10. Yer is a bit tedious this part
Well it was Craptor (factor) theorem

t^2(3-2t) + 4=0
So yes basically guess work. I'm sure you can set up iterations though
11. (Original post by lexazver203)
How do you know t=2?
That's a good point - I didn't notice what he'd done there. Look at post 51 for a better solution

xyter - I was saying my solution is 14 posts ahead of yours
12. (Original post by XYTER)
I'll do the entire questions and hope its all good!

y=t^2 x =t^3

3y-2x+4=0
Sub in values and get

3t^2 - 2t^3 +4 =0
t^2(3-2t)=-4
therofer t =2
Put t in
y = 2^2=4
x= 2^3= 8 Tah dah!!!!!!!!!!!!
Now we have co ordinates so can we let this quezzy go?
wot on earth r u DOING
t^2(3-2t)=-4, tell me how when t=2, tht satisfies, u keep ****ing up the equation
13. Ah yes you can use iterations but have to mod else it doesnt work
14. (Original post by XYTER)
3t^2 - 2t^3 +4 =0
t^2(3-2t)=-4
therofer t =2 then do the rest U SELF
yes but lookin by your method, how have u obtained tht t=2
15. Well in all honesty its was jsut looking at the eqn and relaising it was 2 but yes Bezza has a far better solution to it He did
3t^2 -2t^3+4=0
used facotr theorem and showed 2 onyl solution so kudos look at post 55
16. (Original post by Bezza)
Sub x = t^3 and y = t^2 into the equation of l and multiply through by (-1) to get 2t^3 - 3t^2 - 4 = 0 By the factor theorem, (t-2) is a factor, taking this out gives (t - 2)(2t^2 + t + 2) = 0 The only real solution is t = 2, point B is (8,4)
Ok Bezza - i am probably being really silly here and someone has proably answered this question - but how do you know that (t-2) is a factor?
17. Bedtime!
18. (Original post by Silly Sally)
Ok Bezza - i am probably being really silly here and someone has proably answered this question - but how do you know that (t-2) is a factor?
from factor theorem, saying (t-2) is a factor of a polynomial means you can divide the polynomial by (t-2) and not get any remainder, i.e. (t-2) is a factor.
you can check this quickly because (t-2=0) therefore let t=2
sub 2 into the equation and it should equal 0

ok, now it's Bedtime!!
19. (Original post by kimoni)
from factor theorem, saying (t-2) is a factor of a polynomial means you can divide the polynomial by (t-2) and not get any remainder, i.e. (t-2) is a factor.
you can check this quickly because (t-2=0) therefore let t=2
sub 2 into the equation and it should equal 0

Bedtime!!
No - wat i mean is how do you look at it and be able to tell that (t-2) is a factor? I mean that seems to me a bit trial and error
20. (Original post by Silly Sally)
No - wat i mean is how do you look at it and be able to tell that (t-2) is a factor? I mean that seems to me a bit trial and error
It is trial and error, you just have to keep sticking numbers in until it equals 0

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