# Math Help - cubic equation curve

1. ## cubic equation curve

Hello all, I searched the web for this answer, could not find it, as such i turn to you all smart people. I have read the thread
Cubic equation from 4 coordinates

However i have no idea what to do, if someone can help me before the end of April would be appreciated.

Ok the question is:

*graph* coordinates that can be known, (0,0) (1,8) (2,6) (3,0) (4,-4) (5,0) and (6,18)

Now the actual question is to find accurately the area enclosed by this curve and the x-axis, but to do it accurately, one would have to use definite integral. However i have used the Trapezium Method and the Triangle area method to kinda get an area, but the question after this one requires this one to be dead accurate

i have battled with it for some time; I have nooooo cooking clue of how to do this....

2. Originally Posted by KarrotBear
Hello all, I searched the web for this answer, could not find it, as such i turn to you all smart people. I have read the thread
Cubic equation from 4 coordinates

However i have no idea what to do, if someone can help me before the end of April would be appreciated.

Ok the question is:

*graph* coordinates that can be known, (0,0) (1,8) (2,6) (3,0) (4,-4) (5,0) and (6,18)

Now the actual question is to find accurately the area enclosed by this curve and the x-axis, but to do it accurately, one would have to use definite integral. However i have used the Trapezium Method and the Triangle area method to kinda get an area, but the question after this one requires this one to be dead accurate

i have battled with it for some time; I have nooooo cooking clue of how to do this....

You can find the area of the polygon defined by the given vertices and the axes, however without specifying what type of curve is to go through the points there is no unique area definable from a set of points.

RonL

3. Hello CB,

He said it was a cubic thing, looks like polynomial of degree 3..

4. Originally Posted by Moo
Hello CB,

He said it was a cubic thing, looks like polynomial of degree 3..
No he did not say it was a cubic, he read a thread about fitting a cubic, that is not the same thing.

If he wants a cubic then he should say so.

RonL

5. He already said, in his other thread, and in the live chat

6. The cubic equation
$x(x-3)(x-5)=0$

seems to satisfy your conditions. If you multiply that out you get
$x^3-8x^2+15x=0$

7. Originally Posted by Moo
He already said, in his other thread, and in the live chat
What other thread? (I expect topsquark deleted it)

And any amplification posted in chat is wasted as most people who might help will never read it.

RonL

8. Yep, it has been deleted... I know for the chat, I just wanted to tell you that it was a cubic equation

9. Originally Posted by Moo
Yep, it has been deleted... I know for the chat, I just wanted to tell you that it was a cubic equation
OK, if it is a polynomial of degree <7, then the 7 point Newton-Cotes formula will give the exact integral.

RonL

10. ## Thank you everyone :)

Sorry for double posting/ spamming (if you really can call it that) didnt know it was against rules.

Well yes it is actualy a cubic function, we're in a public school so what do you expect from questions, they only hint at what it is awell

thank you everyone
I have a massivly COOOOL graphics calculator that did it for me, like i was so stressing and then the teachers like " oh and this is how you get the formula for a cubic"

Icemanfan, how did you find that equation? because i wanna know how you did it

Captian Black your tooo smart, ive got a physics teacher like you knows everything in the world i rekon :P

awell thank you all