5 (b) iv (1 Viewer)

[trickpat23]

Wat was up with 5(b) iv
i have absolutely no idea how we are supposed to do newtons law if we arent estimating the root. We were estimating a pnt of intersection, how does that work

(HSC is scum) cheerio Maths is GOOOOOOOOOOOOOOOOOOONE

 

[The Bograt]

I couldnt do the first part of the question, but I attempted this bit

I got 1.75, though I doubt it's right because it is hardly close to 0.5....

 

[becany]

umm..just use newtons for the x^3 + x - 1...

 

[VVoody]

they gave you x1 = 0.5

you had an equation f(x) = x^3 + x -1 = 0

easy $$

 

[VVoody]

I couldnt do the first part of the question, but I attempted this bit

I got 1.75, though I doubt it's right because it is hardly close to 0.5....

yea, I got something that wasnt close at all....

 

[Jebu]

I can probably lend some aid here, as i was having the same problem as you were last night Brett, in fact i think i tried to explain it to you this morning. The formula is:

x(2) = x - f(1) / f'(1)

Eg, closer root x(2) = current estimate 0.5 - f(0.5)/f'(0.5)

The thing is, the f(x) has to be evaluated in radians. which means on your calculator: mode mode 2 (rad). Then you should have got something close to 0.5? I cant quite remember. But the thing is that the functions are evaluated in radians, not degrees. Shame we were never really told that, eh.

 

[acmilan]

Why would it have to be in radians, it didnt involve trig. I got about 0.7 for this i think

 

[withoutaface]

Yes the answer was .7

 

[Sweet_Lemon]

got 0.74 something like tat or 0.71...can't remember~

 

[acmilan]

complete answer was 0.714285714...

 

[jiegu]

0.714285714 i got that too was easy one i think

 

[smallcattle]

they gave you x1 = 0.5

you had an equation f(x) = x^3 + x -1 = 0

easy $$

i think you suppose to use the f(x)=1/(1+x^2)

not x^3+x-1=0

 

[VVoody]

Ack!
dfsdfsdfsdfsdf

 

[phungus]

0.71 nice

 

[bevstarrunner]

for iv, said it was a root coz they intersect when y=x...??
ie. x = 1/(1 + x²)
which gets you to the x³ + x - 1 = 0

is that right..?

 

[Dougie]

um....
i've never heard of doing it like that...

 

[bevstarrunner]

well I had nfi, and i saw that link...

anyone wanna tell me how to actually do it then??

 

[mishka]

yay!! was that worth one or two marks?? i can't remember... i think it was two!!

that's at least 2/84 then!!!

jks

 

[gerardk]

i dunno if it was right or not but i threw in x=1 and x=0 and since change in sign a root lies between 0 and 1...then i just cunningly stated alpha was a root

 

[gordo]

u know the intersection lies on y = x
and for the newton u use the eqn they gave u in the part before it and get 0.7 or something