Aleksas Domarkas <aleksasd873 at gmail.com> writes:
> (%i1) load(solve_rat_ineq)$
> (%i2) ineq:(x^2-x-6)/(x^2-7*x+12)<0;
> (%o2) (x^2-x-6)/(x^2-7*x+12)<0
> (%i3) solve_rat_ineq(ineq);
> (%o3) [[x>-2,x<4]]
>
> Is x=3 solution?
>
> (%i4) subst(x=3,ineq);
> expt: undefined: 0 to a negative exponent.
> -- an error. To debug this try: debugmode(true);
Er, yes. But the quotient is actually (x+2)/(x-4). Subst just
substituted in the zero literally and you got 0/0. Try ratsubst:
(%i5) ratsubst(3,x,ineq);
(%o5) - 5 < 0
Rupert
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