indeterminate coefficients

pl. Math .: A method of analysis invented by Des cartes, the principle of which consists in this, that if we have an equation of this form A+B+Cx2+D.x3+ .=0, in which the coefficients A, B, C, D, ., are constant, and za variable quantity, which may be supposed as small as we please, then each of these coefficients taken separately is nece arily equal to 0.