Question

This is not hard, please help!!! Anyone good at math?

Answer 1

\[f(x)=x^3-x+7\]I was offered http://web.mit.edu/10.213/www/extra/solvecubic.pdf
and I tried to ask that using method 1 V=0
but 0 is one of the zeros of this function.

Answer 2

not its not

Answer 3

0^3-0+7 = 7 not 0

Answer 4

Yeah, my bad.
it's all that function over 1 right?

Answer 5

?

Answer 6

Alright, if my question really didn't make sense just now.

\[1~~/~~(~AV^3+BV^2+D~)\]so far right?

Answer 7

B/c C=-1

Answer 8

wiki cubic function
scroll down to Cardano's method

Answer 9

I am totally not getting this staff, can someone work it, or a similar problem with me?

Answer 10

@Kainui !!! TNX god a helper is here, can you show me how to do method 1 in this link? http://web.mit.edu/10.213/www/extra/solvecubic.pdf

Answer 11

I'm looking at it now and I'm curious, but I think I have my own method of solving cubics that involves complex numbers... Give me a second to play around with this new method I've never seen it before.

Answer 12

OK

Answer 13

After you see this method, can you show me in detail how to do it, please

Answer 14

You want to do it this way or what's your motivation, since method 3 on that same page looks like the most fun.

Answer 15

Lets start from method 1, if you will, @Kainui.

Answer 16

I think I understand the first method more or less, but it would be a pain in the butt to do it on paper. This whole paper seems to be more geared towards programming and doing it on the computer rather than by hand.

Answer 17

So you don't want to do method 1, what about method 2?

Answer 18

The first method is about making a guess and doing many iterations that will continually get closer and closer to an approximation of the answer.

Method 2 seems to be pretty straight forward. Open up Microsoft Excel and follow the instructions step by step. I'll help you out if that gives you issues.

Answer 19

1st method sucks.

2nd method, please help.

Answer 20

Sure, so open up Excel and let's walk through it.

Answer 21

I should open an excel? alright, but you can use latex for chart too.
Whatever you want.

Answer 22

Opened.

Answer 23

Alright so in A1 type: V
A2: 10
B1: f(V)=0
B2:A2^3-8*A2^2+17*A2-10

Answer 24

Just copy and paste each thing into each cell.

Answer 25

Note that by typing A2 in an equation in a cell, it acts like a variable, replacing that variable with the value in cell A2. When the value in cell A2 is a root of f(V), then cell B2 will be 0.

Answer 26

You're either with me or you aren't at this point.

Answer 27

My head is not working correctly right now, sorry, I am sure we can continue this later , if you can.....

Answer 28

Yeah definitely, take a nap or something and just look at that second method on the pdf you showed me. Follow the steps exactly, and it'll get you there.

Answer 29

If I'm here, I'll try to help.

Answer 30

TY, and I'll be able to know if you are at any time... again, ty so much!

Answer 31

I have Excel 2010 and the "Goal Seek" was found under "Data" tab > "What-If Analysis" > "Goal Seek".

Answer 32

I have LibreOffice4.1.
It's a unique thing, it's one program that has excel word doc and everything I need.

Answer 33

For the cubic equation, x^3 - x + 7, Excel quickly found a root at x = -2.08673.

The first method does not converge towards the root no matter what the starting value is: positive, negative or zero.

Answer 34

Online calc is not my goal, I'll later continue this.

Answer 35

calc- calculator.