#math/linear-algebra #math/pde #flashcards/math
A function $f:D\subseteq\mathbb{R}^n\to\mathbb{R}$ is **homogeneous of degree $k$** if %%::%%
$
f(\lambda x)=\lambda^k f(x)
$
for every $x\in D$ and every scalar $\lambda$ for which $\lambda x\in D$ and $\lambda^k$ is defined.
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For [[2A2 - Polynomials|polynomials]], a polynomial is homogeneous when every monomial has the same total degree. For example,
$
f(x,y)=x^3+x^2y+xy^2+y^3
$
is homogeneous of degree $3$, because
$
f(\lambda x,\lambda y)
=(\lambda x)^3+(\lambda x)^2(\lambda y)+(\lambda x)(\lambda y)^2+(\lambda y)^3
=\lambda^3f(x,y).
$