(1) Find the value range of k?
(2) Is there a real number k that makes the reciprocal sum of the two real number roots of the equation equal to 0? If it exists, find the value of k; If it does not exist, explain why.
2. (Zhanjiang, Guangdong, 20 10) The patient took a certain drug according to the prescribed dose, and the blood content per milliliter reached the maximum of 4 mg 2 hours after taking the drug. It is known that the content of Y (mg) per milliliter of blood 2 hours ago is directly proportional to the time x (hours) after taking the medicine. After 2 hours, y is inversely proportional to x (as shown). Answer the following questions based on the above information:
(1). Find the functional relationship between y and x when 20≤≤x;
(2) If 2> is X, the functional relationship between Y and X;
(3) If the treatment is effective when the blood content per milliliter is not less than 2mg, take the medicine once. How long is the effective time to treat the disease?
1. What are the five subjects in the special edition exam?
There are five courses, namely three public courses and two professional courses. Profession