Polynomials are expressions like $15x^3 - 14x^2 + 8$. Questions tagged with this concern common operations on polynomials, like adding, multiplying, polynomial long division, factoring and solving for roots.

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Taylor series and differentiation

The Taylor series about 0 for the function $$f(x) = \left(\frac14 + x\right) ^ {-\frac{3}{2}}$$ is $$f(x) = 8 - 48x+240x^2-1120x^3 + \dots$$ for $-\frac{1}4 < x <\frac14$ Use differentiation ...
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Finding the underlying model from data

Let's say I have "k" data points in "n" dimensions. I also have "k" results of an unknown function of this data. Is it possible, simply given the data and the results from the function, to guess the ...
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1answer
24 views

Determining the intersection of an arbitrary number of polynomials.

Say $f_1,f_2,\dots,f_k\in k[x_1,x_2,\dots,x_n]$, where $k$ is a field. Clearly, every $f_i$ is a polynomial. How does one represent the intersection of all these polynomials? In other words, I want ...
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Finding the leading exponent of a binary number

Let's say that the binary representation of a number $k$ is $2^{X_n} + 2^{X_{n-1}} + \dots + 2^{X_0}$ with each term in this polynomial having a $1$ or $0$ multiplied to it (I just haven't showed them ...
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Representing multivariable polynomials as matrices

Is there a nice way to represent polynomials in $x$ and $y$ of degree say $n$ as matrices, so that multiplication works out in a nice way? Maybe a ring homomorphism or something? I'm sorry that this ...
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29 views

Is the intersection of polynomials in $n$ degrees a polynomial? [on hold]

I have been told that the intersection of two polynomials is a polynomial. Given two polynomials in $n$ variables, how do I represent their intersection? I initially thought it would be $f-g$. ...
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1answer
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Always “one double root” between “no root” and “at least one root” ? (Second version)

Let $a<b$ be two real numbers. Let $f(x,y)$ be a bivariate polynomial. Suppose that $f(x,.)$ has no real roots in the interval $[a,b]$ when $x<0$, but has at least one real root in the interval ...
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Always a double root between “no roots” and “at least one root”?

Let $f(x,y)$ be a real bivariate polynomial. Suppose that $f(x,.)$ has no real roots when $x<0$, but has at least one real root when $x>0$. Does it automatically follow that $f(0,.)$ has a ...
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40 views

Explicit expression for polynomial recurrence relation.

I am (as here) working on Machin formula and with some works I'd like to explore the following polynomial recurrence relation : $$P_0 = 1, P_1 =b,\quad P_{n+2} = XP_{n+1} - P_n$$ It seems relation ...
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Euclidean division - For what values of a, does the polynomial g(t) get divided by f(t) in the complex ring

They want to find the values of a where g(t) can be divided by f(t). $f(t) = t^2 + it − ai$ $g(t) = t^4 + (1 − i)t^3 + (1 − 2i)t^2 − 3at − (4 + 2i)a$ Euclidean algorithm: $g(t) = f(t)q(t) + ...
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Roots of polynomial of degree 6

I'm struggling to find the complex roots of $x^6-9x^3+8 = 0$. I've managed to find the real roots (1 and 2) by letting a variable, say $α = x^3$ and substituting where relevant, leading to a ...
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50 views

Polynomial of degree 5 divisible by other polynomials.

I need some help with a problem. Find a polynomial $f(x)$ of degree $5$ such that both of these properties hold: $f(x)-1$ is divisible by $(x-1)^3$. $f(x)$ is divisible by $x^3$. I can't seem to ...
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Polynomial $f(x)$ degree problem.

Suppose the polynomial $f(x)$ is of degree $3$ and satisfies $f(3)=2$, $f(4)=4$, $f(5)=-3$, and $f(6)=8$. Determine the value of $f(0)$. How would I solve this problem? It seems quite complicated... ...
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25 views

How to solve the inequality: $\prod_{k=1}^N\left(x^k-k^2\right)\gt0$

Given the inequality: $$\displaystyle\prod_{k=1}^N\left(x^k-k^2\right)\gt0$$ how can I solve it? I suppose there is a difference if $N=2n$ or $N=2n+1$ with $n\in\mathbb{N}$, but I'm unable to find a ...
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125 views

A question about algebraically closed fields

A field $\mathbb{K}$ is said to be algebraically closed in practice if every polynomial over $\mathbb{K}$ of positive degree less than or equal to $10^{10}$ has zero belonging $\mathbb{K}$. The ...
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prove $\sum\limits_{cyc} \frac {a^3} {b+c+d} \geq \frac {1} {3}$

Show that if $a,b,c,d \geq 0$ and $ab+bc+cd+da=1$ :$$\sum\limits_{cyc} \frac {a^3} {b+c+d} \geq \frac {1} {3}$$ yet again it should be solved with Cauchy inequality. thing i have done so far: ...
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How to prove $\sum_{i=1}^k(\frac{1}{\alpha_i}\prod_{j\neq i}^k\frac{\alpha_j}{\alpha_j-\alpha_i})=\sum_{i=1}^k\frac{1}{\alpha_i}$?

How to prove $\sum_{i=1}^k(\frac{1}{\alpha_i}\prod_{j\neq i}^k\frac{\alpha_j}{\alpha_j-\alpha_i})=\sum_{i=1}^k\frac{1}{\alpha_i}$? Where $\alpha_1, \alpha_2,\ldots, \alpha_k$ are $k$ distinct ...
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Polynomial Division - “Define the largest natural number…” [on hold]

Would someone mind helping me with this question? The more detailed possible so I can have 100% of understanding. Thanks. Question: Define the largest natural number m such that the polynomial ...
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1answer
27 views

Sum of nth powers and generalized polynomial sum

So this is a 2-part question (both parts I believe are closely related): How exactly does on express the sum $$\sum_{i=0}^{k}{i^n} = Q(n,k)$$ in a closed form For arbitrary positive integers ...
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48 views

Please help me with this problem on binomial expansion [on hold]

Please simplify this expression $\frac{n-r+1!}{n-r-1!}$ I have read the textbook and seen examples but I still do not understand.
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poles of a polynomial

What are the poles of a polynomial? Are they the same as the roots?
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24 views

polynomial factorization and equation solving

Given a polynomial equation: $$x^4+Ax^3+(B+C+D)x^2+(AB+AC)x^2+BD=0$$ where $A$, $B$, $C$, $D$ are known. Numerically I know it has complex solutions. However, I tried but failed to analytically ...
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Polynomial representation

Why is the polynomial $P(x)$ represented as $$ P(x) = a_n x^n + a_{n-1} x^{n-1} + a_{n-2} x^{n-2} + \cdots+ a_2 x^2 + a_1 x + a_0 \text{ ?}$$ A polynomial can be $5x^4 + 3x^3 + 7x^2 + 10x -2$ and it ...
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How do you solve part (b) to this polynomial interpolation question?

(a) Approximate $f'(x_0)$ and $f''(x_0)$ using the values $x_0-h$, $x_0$ and $x_0 + \alpha h$ $(0 < \alpha)$ by applying the polynomial interpolation method. (b) Assuming $f(x)\in C^3$, evaluate ...
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1answer
101 views

$\forall x \,\exists k$ s.t. $f^{(k)}(x)=0$, then $f$ is a polynomial

My friend sent me the following problem: Suppose that $f$ is real analytic on $(a,b)$, and that for all $x$ in $(a,b)$ there exists a non-negative integer $k$ such that $f^{(k)}(x)=0$. Show ...
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1answer
22 views

Product of Chebyshev polynomials of the second kind?

So Wikipedia has this formula for a product of two Chebyshev polynomials of the second kind evaluated at a fixed $x$ with different indices: $$ U_n(x)U_m(x)=\sum_{k=o}^{n}U_{m-n+2k}(x) $$ Which would ...
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A Question about the Proof of Eisenstein's Irreducibity Criterion

Statement: Let $f(x) = a_n x^n + a_{n-1} x^{n-1}+ \cdots + a_0 \in \mathbb Z[x]$. If there is a prime $p$ such that $p \nmid a_n, p \mid a_{n-1}, \dots,p \mid a_0$ and $p^2 \nmid a_0 $, then $f(x)$ ...
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primitivity of a polynomial over a field

Suppose that we have a polynomial $f(x)=ax^3-bx^2+cx-d\in\mathbb{Z}[x]$ then $f(x)$ will be called primitive if $(a,b,c,d)=1$ I have been told that over a field $F$ there is no notion of ...
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How prove that: $\left | a \right |+\left | b \right |\leq 5$ for $P(x)=x^{3}+ax^{2}+bx+1$?

Let $P(x)=x^{3}+ax^{2}+bx+1$ and $\left | P(x) \right |\leq 1$ for all x such that $\left | x \right |\leq 1$. How prove that: $\left | a \right |+\left | b \right |\leq 5$?
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Find scaling factor that minimizes f(x) - round(f(x))?

Let's say I have a function $f(x)$, which has a fractional component $\{ f(x) \} = f(x) - \lfloor f(x) \rfloor$. I would like to add a scaling factor $h(x)$, where $h(x)$ is a polynomial, such that ...
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Whether $\sum_{i=1}^k\frac{\prod_{j\neq i}(\alpha_j-\beta)}{\prod_{j\neq i}(\alpha_j-\alpha_i)}=1$ is true

Suppose we have k positive numbers: $\alpha_1, \alpha_2, ..., \alpha_k$, for any number $\beta>0$, is $$\sum_{i=1}^k\frac{\prod_{j\neq i}(\alpha_j-\beta)}{\prod_{j\neq i}(\alpha_j-\alpha_i)}=1$$ ...
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Differentiability of polynomials

Trivial question but I am confused with the notation If $p_{n-1}$ is a polynomial of degree $n-1$, is it $\in$ the differentiability class C^n$? Obviously if $p_n$ is a polynomial of degree $n$, ...
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A question from the mod p irreducibility test's proof

Let $p$ be a prime an suppose that $f(x) \in \mathbb Z[x]$ with $\deg f(x) \geq 1$. Let $f_1(x)$ be the polynomial in $\mathbb Z_p[x]$ obtained from $f(x)$ by reducing all the coefficients of $f(x)$ ...
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Multivariate Polynomials Sage

Sorry if I'm in the wrong Stackexchange (but sage is a math program...) I'm computing something on multivariate polynomials: I have a primary variable $x$ and several other variables $a, b, c, ...
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51 views

If $a^2=b^2+c^2$ and $0<n<2$ prove $a^n<b^n+c^n$

If $a^2=b^2+c^2$ and $a,b,c$ are positive real numbers, prove (a) if $n>2$ then $a^n>b^n+c^n$, (b) if $0<n<2$ then $a^n<b^n+c^n$. Part (a) was easy to prove: $a^2=b^2+c^2$ and ...
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Find a basis and state its dimension of a $C$-vector space polynomial.

The $C$ vector space $V$ of polynomials $P(t) \in C[t]$ of degree at most $n$ and such that $P(a) = P'(a) = 0$ for $a \in C$ fixed. Indication : prove that $P(t) \in V \Leftrightarrow (t − a)^2$ ...
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Changing the order of the elements of the divided difference Polynomial Interpolation

Apparently this is rather trivial but I don't understand why what I've highlighted in green is correct.
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roots of a polynomial inside a circle

I am asked to show that for $n$ larger or equal to $2,$ the roots of $1 + z + z^{n}$ lie inside the circle $\|z\| = 1 + \frac{1}{n-1}$ Attempt1: Induction for the case $n = 2,$ the roots of $1 + z + ...
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How do you solve the coefficients of functions of two variables as part of 2nd order polynomial?

I'm having a major issue in trying to get my head around creating a formula for the graph ΔT=f(V,W) I already have two graphs for that, but they are 2D graphs. Both represent ΔT as Y but one graph ...
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31 views

Linear Equation as matrix

Using a series of 3x3 matrices multiplied together, it is possible to create a matrix which will rotate, translate, scale and invert a size 2 vector. Using a 4x4, it is possible to do this to a size ...
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1answer
31 views

Primitive-recursive functions and polynomial equations

I am looking for examples of primitive-recursive functions $f:\mathbb{N}\rightarrow\mathbb{N}$ that can not be written as a pair of polynomials, i.e. $$f(n) = m \Leftrightarrow P(n,m) = Q(n,m)$$ ...
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Is $2x^2+4$ reducible over $\mathbb C$?

I am not sure if I making some very fundamental mistake. But Gallian says that $2x^2+4$ is reducible over $\mathbb C$. If $D$ be an integral domain. A polynomial $f(x)$ from $D[x]$ is said to be ...
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How find the polynomial whose roots are $\frac{{a^2 }} {{2a^2 + bc}},\frac{{b^2 }} {{2b^2 + ca}},\frac{{c^2 }} {{2c^2 + ab}}$?

a,b,c are the roots of the polynomial $x^3 - (a + b + c)x^2 + (ab + bc + ca)x - abc$. How find the polynomial whose roots are $\frac{{a^2 }} {{2a^2 + bc}},\frac{{b^2 }} {{2b^2 + ca}},\frac{{c^2 }} ...
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About the subspace of polynomial vector space

Why the set of functions in $C\left [ 1,-1 \right ]$ such that $f\left ( -1 \right )= f\left ( 1 \right )$ is the subspace of $C\left [ 1,-1 \right ]$?
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Is there a reason for some polynomial quotients to have a remainder equals to zero?

I was helping some highschool students with factorization exercises. They had alternatives to choose the correct factor. Then one of them said to me: We use a calculator and evaluate some prime ...
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Problems from Polynomial Rings. My attempt shown.

$1.$ Let $f(x) =a_mx^m+a_{m-1}x^{m-1}+ \cdots +a_0$ and $g(x) = b_nx^n+b_{n-1}x^{n-1}+ \cdots +b_0$ belong to $\mathbb Q[x]$ and suppose that $f \circ g \in \mathbb Z[x].$ Prove that $a_ib_j$ is an ...
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Finding a polynomial's constant from its points

Let's say I was given a set of $d+1$ distinct points known to be from a polynomial $P$ of degree $d$. So: $$P = a_dx^d + a_{d-1}x^{d-1} + ... a_1x + c$$ And I have pairs $(x_i, y_i)$ such that: ...
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What basis and coordinate system is used in this quadratic Bézier triangle equation? $[x,y,z] = A*s^2 + B*t^2 + C*u^2 + D*2st + E*2tu + F*2su$

I have the following equation for a quadratic Bézier triangle, but I'm having a lot of trouble understanding how to describe it: $[x,y,z] = A*s^2 + B*t^2 + C*u^2 + D*2st + E*2tu + F*2su$ ...
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Roots Of Monic Cubic

I'm currently preparing for the USA Mathematical Talent Search competition. I've been brushing up my proof-writing skills for several weeks now, but one area that I have not been formally taught about ...
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Prove that no polynomial function represents a given sequence

I recently encountered the following question: How to find the $n$th term of the sequence $2,3,6,7,14,15,30,\dots$? I replied to that post, and gave the following answer: $S_n = ...