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sunny19821-Visitor
1-Visitor
Nov 2, 2014 8:11 PM UTC
Solved

MathCad help

Hi folks wondering if you can help me? I am using mathcad to solve polynomial equation. I have attempted the question and wanted to see if the question is correct and I am doing what is asked of me. I have to solve it in two different ways other than graphical. I have tried to solve it this way first. Basically h(x)=6 to four decimal places. The answer is in the uploaded file. Would be grateful for some insight.


b) Using MathCad solve the polynomial h(x) = 6 using at least two different methods other than graphical, giving your answers to 4 decimal places........ h(x)=x4-x3-19x​2-11x+30

Werner_E
Werner_EAnswer
25-Diamond I
Nov 2, 2014 10:00 PM UTC

Salim Ahmed wrote:

Gentlemen Thankyou so much, so my method is correct and then I would use werners method and that question would be correct wouldn't it guys?

I would rather do it without the float modifier and evaluate X in a separate region as Mike has done. The reason is that using float you actually lose precision. "float" is not just for display but actually affects the values. Furthermore float,4 gives you 4 significant digits while you need 4 decimals!

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25 replies

MikeArmstrong1-Visitor
1-Visitor
Nov 2, 2014 8:40 PM UTC

How about symbolically?

Clipboard01.jpg

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sunny19821-VisitorAuthor
1-Visitor
Nov 2, 2014 8:44 PM UTC

This is the orignal polynomial h(x)=x4-x3-19x​2-11x+30, because h(x)=6 I minused 6 from 30 which left me with 24. So now I am confused?

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Werner_E
Werner_E25-Diamond I
25-Diamond I
Nov 2, 2014 9:42 PM UTC

Salim Ahmed wrote:

This is the orignal polynomial h(x)=x4-x3-19x​2-11x+30, because h(x)=6 I minused 6 from 30 which left me with 24. So now I am confused?

So am I because I don't understand why you are confused and what confuses you.

Both you and Mike solved the correct equation (original polynomial function - 6 = 0)

I wouldn't have named the polynomial decrease by 6 h(x), too, but thats another story.

Anyway you had found a way using polyroot to get all four solutions and Mike showed you a different way using the symbolic solve command. Both methods yield the same results (but in slightly different order).

So what on earth are you confused about?

1.png

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