k = xn+y = = & gt； (xn+y)？ -4(xn+y)+5=n？ + 1
x？ = 1, = = & gtX= 1 or x=- 1.
2xy-4x=0，
y？ -4y+5= 1，= = & gty=2
= = & gt
x= 1，y=2
= = & gtk=n=2
In addition, the mathematical method also includes:
1. Special value test method:
For a general mathematical problem, we can specialize the problem in the process of solving it, and use the principle that the problem does not hold in special circumstances and does not hold in general circumstances to achieve the purpose of removing the false and retaining the true.
2. Extreme principle:
Analyze the problem to be studied to the extreme state, so that the causal relationship becomes more obvious, thus achieving the purpose of solving the problem quickly. Extreme value is mainly used to find extreme value, range and analytic geometry. Many problems with complicated calculation steps and large amount of calculation can be solved instantly once extreme value analysis is adopted.
3. Elimination method:
Using the information provided by the known conditions, three wrong answers are eliminated from the four options, so as to achieve the purpose of correct selection. This is a common method, especially when the answer is a fixed value or has a numerical range, taking special points instead of verification.
4. Number-shape combination method;
According to the conditions of the topic, make a graph or image that conforms to the meaning of the topic, and get the answer through simple reasoning or calculation with the help of the intuition of the graph or image. The advantage of the combination of numbers and shapes is intuitive, and you can even measure the result directly with a square.
5. Recursive induction:
Through the conditional reasoning of the topic, we can find the law and sum up the correct answer.
6. Forward pyrolysis method:
Using mathematical theorems, formulas, rules, definitions and questions, the method of obtaining results through direct calculus and reasoning.
7. Reverse verification method
(Alternative Answer): A method of verifying all the selected answers, thereby denying the wrong answer and obtaining the correct answer.
8. If there are difficulties, it will violate the law:
When it is difficult to solve the problem from the front, we can find a qualified conclusion step by step from the answer, or draw a conclusion from the opposite side.
9. Characteristic analysis method
Analyze the characteristics of setting questions and choosing answers, find out the rules and summarize the methods of correct judgment.
10. Appraisal selection method:
Some problems cannot (or are not necessary) be accurately calculated and judged due to the limitation of subject conditions. At this time, we can only get the correct judgment method from the surface by means of estimation, observation, analysis, comparison and calculation.