Method of substitution, the most comprehensive multiple-choice mathematical problem-solving skill in the history of college entrance examination, often gives some conditions, such as a greater than or equal to 0 and less than or equal to 1. B is greater than or equal to 1 and less than or equal to 2. Considering some special circumstances, it may be complicated for you to find some formulas for combining ab. But if it is a multiple-choice question, you can try a=0.5 and b= 1.5. There is also a formula that can bring the answers in the options to the questions for calculation. Backward method!
Masking skills of multiple choice questions in mathematics: the golden mean means that the index value takes precedence over the "intermediate quantity" option, and the option takes precedence over bcd. On the same topic, give priority to the "intermediate quantity" of the value and then consider the option bcd. (If the numerical value corresponding to option E is the intermediate value, the numerical value will be considered first. Options such as "None of the above results are correct" will not be considered. From the beginning of extracting the given information, the error is eliminated through the option function. The basic characteristics of the options are as follows:
Single-valued and multi-valued (such as "even power, absolute value, symmetry and other results appear multi-valued) positive and negative values (excluding negative values according to the pre-test question p 12/25) (3) zero and zero.
Super-quasi-college entrance examination math problem-solving skills 1, the last question of conic curve is often difficult to work out. At this time, the special value method can be used to solve the process forcibly, that is, the solution is solved first, and then the delta is calculated. With Vieta's theorem, list the expressions needed for the problem, and it's ok.
2. The space geometry of the required mathematics questions in the college entrance examination is a step in the proof process. I really can't think of directly writing unused conditions and then drawing unexpected conclusions. If the first question really can't be written directly, the second question can be used directly! Candidates who use conventional methods suggest that a spatial coordinate system should be established first. If you make a mistake, you can get at least a few points. This is an opportunistic skill, but it's like crossing a point!
3. There is a step in the process of space geometry that I really can't think of directly writing unused conditions and then drawing unexpected conclusions. If the first question really can't be written directly, the second question can be used directly! Students who use conventional methods suggest that a spatial coordinate system should be established at will first. If you make a mistake, you can get 2 points!
4. A new method to find dihedral angle b-oa-c in solid geometry. Using cosine theorem of trihedral angle. Let dihedral angle b-oa-c be ∠oa, ∠aob be α, ∠boc be β and ∠aoc be γ. This theorem is: cos ∠ OA = (cos β-cos α cos γ)/sin α sin γ. Knowing this theorem, if you encounter the problem of finding dihedral angle in solid geometry in the exam, you will come up with a set of formulas. It is not too late. Try it?