One embodiment of the present invention provides a
system for finding the roots of a polynomial or a quadratic equation with interval coefficients. The
system operates by receiving a representation of a polynomial equation, which can be a quadratic equation of the form F(x)=Ax2+Bx+C=0, wherein A=[AL, AU], B=[BL, BU] and C=[CL, CU] are interval coefficients. Next, the
system computes intervals containing roots of the functions F1(x), F2(x), F3(x) and F4(x), wherein F1(x)=ALx2+BLx+CL, F2(x)=AUx2+BUx+CU, F3(x)=ALx2+BUx+CL and F4(x)=AUx2+BLx+CU. The system then places the computed intervals into a
list, L, and orders the computed intervals in L by their left endpoints, so that for a each entry, Si=[SiL, SiU], SiL≦Si+1,L. Next, the system establishes interval roots for F(x) from the interval entries in
list L. In one embodiment of the present invention, establishing interval roots from the
list L involves: establishing one interval root, [S1,L, S2U], if L contains two entries, S1 and S2; establishing two interval roots, [S1,L, S2U], and [S3L, S4U], if L contains four entries, S1, S2, S3 and S4; and establishing three interval roots, [−∞, S2U], [S3L, S4U] and [S5L, +∞], if L contains six entries, S1, S2, S3, S4, S5 and S6.