My problem is to find a procedure that gives coefficients which make certain functional expression vanishing.
For example if I have a polynomial $P(x)$ of one variable $x$ given by $P(x)=a_0+a_1 x+a_2 x^2...$ I would like Mathematica to give $a_i=0$ as the solution to $P(x)=0$. Or consider more complicated example which is closer to the real task I'm dealing with. Suppose I have equation $a_1 K(x)+a_2 E(x)=0$ where $K,E$ are elliptic integrals. It only matters here that they are linearly independent functions of $x$, so the there is the unique solution $a_1=a_2=0$. Of course In the case with polynomial one can just require to vanish Coefficient[$P(x),x^i$]. Similarly, one can expand $a_1 K(x)+a_2 E(x)$ in powers of $x$ and find $a_1,a_2$ which makes several first terms of expansion absent.
But isn't there a more elegant/standard way to handle this task? I would like to somehow explain to Mathematica that $a_i$ in these expressions are fixed coefficients while $x$ is a variable and that equations must hold for every $x$ thus giving constraints on $a_i$.