Hello - this is a novice's question: Consider the following: > E1 := a = b > E2 := b = c > eliminate({E1, E2}, {b}) [{b = c}, {a - c}] So this works. > E3 := a1(t) = b1(t) > E4 := b1(t) = c1(t) > eliminate({E3, E4}, {b1}) Error, (in eliminate/recursive) invalid subscript selector What should I do in the second set above to eliminate b1(t) and get the result a1(t) = c1(t)? Thanks.