Construct a polynomial $p$ of degree $leq n-1$ such that $p(a_i) = b_i$











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Theorem. Given two countably infinite sequences of complex numbers ${a_{n}}_{n}$ and ${b_{n}}_{n}$ with $lim_{n to infty}|a_{n}| = infty$, it is always possible to find a entire function $F$ that satisfies $F(a_{n}) = b_{n}$ for all $n$.




First, I want to prove




Problem. If $a_1,dots,a_n$ and $b_1,dots,b_n$ are distinct complex numbers, I can construct a polynomial $p$ of degree $leq n-1$ such that $p(a_i) = b_i$ for all $i=1,dots,n$.




My approach.



$$c_{0} + c_{1}a_{1} + c_{2}a_{1}^{2} + cdots + c_{n-1}a_{1}^{n-1} = b_{1}$$
$$c_{0} + c_{1}a_{2} + c_{2}a_{2}^{2} + cdots + c_{n-1}a_{2}^{n-1} = b_{2}$$
$$vdots$$
$$c_{0} + c_{1}a_{n} + c_{2}a_{n}^{2} + cdots + c_{n-1}a_{n}^{n-1} = b_{n}$$
and so
$$left(begin{array}{ccccc}
1 & a_{1} & a_{1}^{2} & cdots & a_{1}^{n-1}\
1 & a_{2} & a_{2}^{2} & cdots & a_{2}^{n-1}\
vdots & vdots & vdots & ddots & vdots\
1 & a_{n} & a_{n}^{2} & cdots & a_{n}^{n-1}\
end{array}right)
left(begin{array}{c}
c_{0}\
c_{1}\
vdots\
c_{n-1}
end{array}right)
=
left(begin{array}{c}
b_{1}\
b_{2}\
vdots\
b_{n}
end{array}right)$$



What is the best method to solve this system? Or, Is there a better approach to this problem??










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  • 2




    This is called lagrange interpolation.
    – Robert Wolfe
    Nov 19 at 3:45










  • @RobertWolfe, thank you!
    – Lucas Corrêa
    Nov 19 at 3:49






  • 2




    Just like magic - if you the name of something, you gain power.
    – marty cohen
    Nov 19 at 4:20






  • 1




    For the main question see "An Interpoation Problem' in Rudin's RCA. [ Chapter on Zeros of Holomorphic Functions].
    – Kavi Rama Murthy
    Nov 19 at 5:28












  • @martycohen, absolutely! hahaha
    – Lucas Corrêa
    Nov 19 at 16:54















up vote
1
down vote

favorite













Theorem. Given two countably infinite sequences of complex numbers ${a_{n}}_{n}$ and ${b_{n}}_{n}$ with $lim_{n to infty}|a_{n}| = infty$, it is always possible to find a entire function $F$ that satisfies $F(a_{n}) = b_{n}$ for all $n$.




First, I want to prove




Problem. If $a_1,dots,a_n$ and $b_1,dots,b_n$ are distinct complex numbers, I can construct a polynomial $p$ of degree $leq n-1$ such that $p(a_i) = b_i$ for all $i=1,dots,n$.




My approach.



$$c_{0} + c_{1}a_{1} + c_{2}a_{1}^{2} + cdots + c_{n-1}a_{1}^{n-1} = b_{1}$$
$$c_{0} + c_{1}a_{2} + c_{2}a_{2}^{2} + cdots + c_{n-1}a_{2}^{n-1} = b_{2}$$
$$vdots$$
$$c_{0} + c_{1}a_{n} + c_{2}a_{n}^{2} + cdots + c_{n-1}a_{n}^{n-1} = b_{n}$$
and so
$$left(begin{array}{ccccc}
1 & a_{1} & a_{1}^{2} & cdots & a_{1}^{n-1}\
1 & a_{2} & a_{2}^{2} & cdots & a_{2}^{n-1}\
vdots & vdots & vdots & ddots & vdots\
1 & a_{n} & a_{n}^{2} & cdots & a_{n}^{n-1}\
end{array}right)
left(begin{array}{c}
c_{0}\
c_{1}\
vdots\
c_{n-1}
end{array}right)
=
left(begin{array}{c}
b_{1}\
b_{2}\
vdots\
b_{n}
end{array}right)$$



What is the best method to solve this system? Or, Is there a better approach to this problem??










share|cite|improve this question


















  • 2




    This is called lagrange interpolation.
    – Robert Wolfe
    Nov 19 at 3:45










  • @RobertWolfe, thank you!
    – Lucas Corrêa
    Nov 19 at 3:49






  • 2




    Just like magic - if you the name of something, you gain power.
    – marty cohen
    Nov 19 at 4:20






  • 1




    For the main question see "An Interpoation Problem' in Rudin's RCA. [ Chapter on Zeros of Holomorphic Functions].
    – Kavi Rama Murthy
    Nov 19 at 5:28












  • @martycohen, absolutely! hahaha
    – Lucas Corrêa
    Nov 19 at 16:54













up vote
1
down vote

favorite









up vote
1
down vote

favorite












Theorem. Given two countably infinite sequences of complex numbers ${a_{n}}_{n}$ and ${b_{n}}_{n}$ with $lim_{n to infty}|a_{n}| = infty$, it is always possible to find a entire function $F$ that satisfies $F(a_{n}) = b_{n}$ for all $n$.




First, I want to prove




Problem. If $a_1,dots,a_n$ and $b_1,dots,b_n$ are distinct complex numbers, I can construct a polynomial $p$ of degree $leq n-1$ such that $p(a_i) = b_i$ for all $i=1,dots,n$.




My approach.



$$c_{0} + c_{1}a_{1} + c_{2}a_{1}^{2} + cdots + c_{n-1}a_{1}^{n-1} = b_{1}$$
$$c_{0} + c_{1}a_{2} + c_{2}a_{2}^{2} + cdots + c_{n-1}a_{2}^{n-1} = b_{2}$$
$$vdots$$
$$c_{0} + c_{1}a_{n} + c_{2}a_{n}^{2} + cdots + c_{n-1}a_{n}^{n-1} = b_{n}$$
and so
$$left(begin{array}{ccccc}
1 & a_{1} & a_{1}^{2} & cdots & a_{1}^{n-1}\
1 & a_{2} & a_{2}^{2} & cdots & a_{2}^{n-1}\
vdots & vdots & vdots & ddots & vdots\
1 & a_{n} & a_{n}^{2} & cdots & a_{n}^{n-1}\
end{array}right)
left(begin{array}{c}
c_{0}\
c_{1}\
vdots\
c_{n-1}
end{array}right)
=
left(begin{array}{c}
b_{1}\
b_{2}\
vdots\
b_{n}
end{array}right)$$



What is the best method to solve this system? Or, Is there a better approach to this problem??










share|cite|improve this question














Theorem. Given two countably infinite sequences of complex numbers ${a_{n}}_{n}$ and ${b_{n}}_{n}$ with $lim_{n to infty}|a_{n}| = infty$, it is always possible to find a entire function $F$ that satisfies $F(a_{n}) = b_{n}$ for all $n$.




First, I want to prove




Problem. If $a_1,dots,a_n$ and $b_1,dots,b_n$ are distinct complex numbers, I can construct a polynomial $p$ of degree $leq n-1$ such that $p(a_i) = b_i$ for all $i=1,dots,n$.




My approach.



$$c_{0} + c_{1}a_{1} + c_{2}a_{1}^{2} + cdots + c_{n-1}a_{1}^{n-1} = b_{1}$$
$$c_{0} + c_{1}a_{2} + c_{2}a_{2}^{2} + cdots + c_{n-1}a_{2}^{n-1} = b_{2}$$
$$vdots$$
$$c_{0} + c_{1}a_{n} + c_{2}a_{n}^{2} + cdots + c_{n-1}a_{n}^{n-1} = b_{n}$$
and so
$$left(begin{array}{ccccc}
1 & a_{1} & a_{1}^{2} & cdots & a_{1}^{n-1}\
1 & a_{2} & a_{2}^{2} & cdots & a_{2}^{n-1}\
vdots & vdots & vdots & ddots & vdots\
1 & a_{n} & a_{n}^{2} & cdots & a_{n}^{n-1}\
end{array}right)
left(begin{array}{c}
c_{0}\
c_{1}\
vdots\
c_{n-1}
end{array}right)
=
left(begin{array}{c}
b_{1}\
b_{2}\
vdots\
b_{n}
end{array}right)$$



What is the best method to solve this system? Or, Is there a better approach to this problem??







complex-analysis interpolation






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Nov 19 at 3:44









Lucas Corrêa

1,252321




1,252321








  • 2




    This is called lagrange interpolation.
    – Robert Wolfe
    Nov 19 at 3:45










  • @RobertWolfe, thank you!
    – Lucas Corrêa
    Nov 19 at 3:49






  • 2




    Just like magic - if you the name of something, you gain power.
    – marty cohen
    Nov 19 at 4:20






  • 1




    For the main question see "An Interpoation Problem' in Rudin's RCA. [ Chapter on Zeros of Holomorphic Functions].
    – Kavi Rama Murthy
    Nov 19 at 5:28












  • @martycohen, absolutely! hahaha
    – Lucas Corrêa
    Nov 19 at 16:54














  • 2




    This is called lagrange interpolation.
    – Robert Wolfe
    Nov 19 at 3:45










  • @RobertWolfe, thank you!
    – Lucas Corrêa
    Nov 19 at 3:49






  • 2




    Just like magic - if you the name of something, you gain power.
    – marty cohen
    Nov 19 at 4:20






  • 1




    For the main question see "An Interpoation Problem' in Rudin's RCA. [ Chapter on Zeros of Holomorphic Functions].
    – Kavi Rama Murthy
    Nov 19 at 5:28












  • @martycohen, absolutely! hahaha
    – Lucas Corrêa
    Nov 19 at 16:54








2




2




This is called lagrange interpolation.
– Robert Wolfe
Nov 19 at 3:45




This is called lagrange interpolation.
– Robert Wolfe
Nov 19 at 3:45












@RobertWolfe, thank you!
– Lucas Corrêa
Nov 19 at 3:49




@RobertWolfe, thank you!
– Lucas Corrêa
Nov 19 at 3:49




2




2




Just like magic - if you the name of something, you gain power.
– marty cohen
Nov 19 at 4:20




Just like magic - if you the name of something, you gain power.
– marty cohen
Nov 19 at 4:20




1




1




For the main question see "An Interpoation Problem' in Rudin's RCA. [ Chapter on Zeros of Holomorphic Functions].
– Kavi Rama Murthy
Nov 19 at 5:28






For the main question see "An Interpoation Problem' in Rudin's RCA. [ Chapter on Zeros of Holomorphic Functions].
– Kavi Rama Murthy
Nov 19 at 5:28














@martycohen, absolutely! hahaha
– Lucas Corrêa
Nov 19 at 16:54




@martycohen, absolutely! hahaha
– Lucas Corrêa
Nov 19 at 16:54















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