% quadratic(A,B,C,Ans):
% Computes the solution(s) to the quadratic formula for A*X^2 + B*X + C = 0
% If coeffs are illegal, or a complex solution, then fails.

quadratic(A, B, C, Ans) :-
	number(A),
	number(B),
	number(C),
	Discr is B*B-4*A*C,
	Discr >= 0,
	quad2(A, B, Discr, Ans).

quad2(A, B, Discr, Ans) :-
	Ans is (-B-sqrt(Discr)) / (2*A).
quad2(A, B, Discr, Ans) :-
	Ans is (-B+sqrt(Discr)) / (2*A).