Reciprocal equation

An equation of the form

$$a_0x^n+a_1x^{n-1}+\dotsb+a_{n-1}x+a_n=0$$

in which the coefficients located at equal distances from the beginning and from the end are equal: $a_i=a_{n-i}$. A reciprocal equation of degree $2n$ may be reduced to an $n$-th degree equation by putting $z=x\pm1/x$.