2. Plane vector is a tool to solve geometric problems. So try to draw pictures when doing plane vector problems. You don't understand the problem correctly. If you only analyze the case of K=0, you will certainly not understand why this is the answer. In fact, draw a picture in this topic, and then remove the irrelevant point O from | OA+(k-1) ob-koc | > | OA-oc | to become | BA-KBC | > | CA |. At this time, it can be seen from the figure that AC is the shortest in the connection line between A and the point on the straight line BC, so AC⊥BC.
You watch first, and I will continue to answer.
You used the word "cheating" in this question. Although it is not appropriate, it can express your desire to score. In fact, multiple-choice questions focus on "choice", so we often don't do it directly, but combine choice with "special value method", "alternative verification method" and "exclusion method" as long as we can get the answer.
You are not very clear about the probability model. It's not clear in one or two sentences here. Let me give you a suggestion. It takes three hours to explain the basic problems clearly, and then it is accompanied by special exercises. This kind of problem is not difficult to break through. Because the distribution list questions in the college entrance examination are mostly intermediate questions, it is easier to score. I hope these three hours can bring you 12 points of "income".
4, of course, is the zero judgment theorem. That is to consider whether the endpoint function value is a different sign, of course, we should combine the selection branch here.
5. Multiplication of four formulas requires taking out a number in each bracket for multiplication, as long as the X term must be generated by taking out X in one bracket and taking out constants in another formula. The answer is not difficult to get. The idea of constant term is the same as above. As for the other information you asked, it will not be involved in this formula. To say the least, if it is involved, it is the same as the above idea. Usually, the rest of the problems you talk about involve binomial theorem.
6. The first question is obviously based on the cosine theorem, and then the mean inequality. Other thoughts are superfluous. This is the basic way of thinking. The second problem is to find the scope. If it becomes marginal, what should be done? Therefore, it is necessary to use the triangle interior angle sum theorem to reduce the angle, simplify the formula into the form of Asin(ωx+φ)+B, and use the properties of sine function to solve it.
According to the question you asked, it should be said that you have a very accurate positioning of yourself. Actually, it's only a few days. I suggest you make a breakthrough in the questions you think you can do, but you can't get points. Then, make sure you can do the right question. You should be able to get around 1 10. Wish you success!