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换元法是解决数学问题的一种常用方法。例如解方程((x-1)~(1/3))~2-3·(x-1)~(1/3)-4=0时,设(x-1)~(1/3)=t,象这种仅用一个字母替换某个式子的换元方法,我们把它称为常规换元法。另外,我们常常遇到或不自觉地使用另一种变换方法,例如在根据椭圆的定义,推导椭圆的标准方程的过程中,设|PF_1|+|PF_2|=2a,以及令 a~2-c~2=b~2;又例如在求函数 y=asinx+6cosx 的最大值、最小值(a、b 不同时为零)的过程中,令
Redemption method is a common method to solve mathematical problems. For example, when (x-1) to (1/3)) ~ 2-3 · (x-1) to (1/3) -4 = = t, such as this one-letter replacement method with only one letter substitution method, we call it a conventional method for the yuan. In addition, we often encounter or unconsciously use another transformation method, for example, according to the definition of the ellipse, derive the standard equation of the ellipse, set | PF_1 | + | PF_2 | = 2a, and make a ~ 2- For example, in the process of finding the maximum value and the minimum value of the function y = asinx + 6cosx (a and b are both nonzero), let