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ptc-67433761-Visitor
1-Visitor
November 10, 2014
Question

find root for function with factors as vector

  • November 10, 2014
  • 3 replies
  • 1484 views

Hi,

For a function which has the factors as vector, how roots can be found.

simple function: f(x)=x^2+c

3 replies

Werner_E
Werner_E25-Diamond I
25-Diamond I
November 10, 2014

M.Reza Karimian wrote:

Hi,

For a function which has the factors as vector, how roots can be found.

What exactly do you mean by that? Which factors?

Better you provide a worksheet and attach it to your post.

P
ptc-67433761-VisitorAuthor
1-Visitor
November 10, 2014

Dear Werner,

For example the function is

f(x)=a x^2+b x+c

and a,b,c are column vector. a=(1,1,1), b=(0,0,0), c=(-10,-20,-30).

for normal function, the root can be found by root(f(x),x,-10,0). But when function f(x) is column vector, it is not solved.

Thank you for your help.

Regards,

Karimian

Werner_E
Werner_E25-Diamond I
25-Diamond I
November 10, 2014

M.Reza Karimian wrote:

Dear Werner,

For example the function is

f(x)=a x^2+b x+c

and a,b,c are column vector. a=(1,1,1), b=(0,0,0), c=(-10,-20,-30).

for normal function, the root can be found by root(f(x),x,-10,0). But when function f(x) is column vector, it is not solved.

Thank you for your help.

Regards,

Karimian

At first - please don't crosspost. You have posted your question additionally in two (very old) threads which is in no way disirable.

You would have to define what "root" should mean in the context of a vector function. Guess you have in mind the the outcome should be the null-vector [0;0;0], right?

Mathcad's root function, as the help also states, is for scalar functions with scalar arguments only. So you probaly would have to use a solve block with find().

BTW, are you aware of the fact that, given that x is 3x1 vector (and otherwise your function would not make much sense as it would mean three equations but just one variable), x^2 is a vector and a x^2 would be a scalar product? The same applies to b*x, it would be a scalar, too.

If I am right with my guess you will have to use vectorisation!

I hope the attached file will be of help.

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