Так?:
Program solution;
Uses Crt;
Var a, b, c : Integer;
s, k, y : Real;
begin
clrscr;
write('a, b, c: ');
readln(a, b, c);
s := (a + c * c * c * c) / (3 * b);
k := s - sqrt(abs(a + 2 * b * c * c * c * c));
y := a + 2 * b - (3 * s) / (b * c);
write(y : 0 : 4);
readkey;
End.