在解题实践中,如何化归,化繁为简、化难为易、化生为熟,其技巧性很强。笔者认为,换元法是实现上述转化的有效方法,举例说明如下。 俐1.解方程(19x-x~2)/(x+1)(x+(19-x)/(1+x))=84. 解 设y=(19-x)/(1+x),则原方程等价于方程组 xy(x+y)=84, xy+(x+y)=19. 则xy,x+y为方程z~2-19z+84=0的两根,进而易于求得xy,x+y的值,再解得 In the problem-solving practice, how to return to the source, to simplify and simplify, to make it difficult to change, to become a mature student, its skill is very strong. The author believes that the rendition method is an effective method to achieve the above transformation, and examples are as follows.俐 1. Solve equation (19x-x~2)/(x+1)(x+(19-x)/(1+x))=84. Solve for y=(19-x)/(1+x) The original equation is equivalent to the system of equations xy(x+y)=84, xy+(x+y)=19. Then xy,x+y are the two equations z~2-19z+84=0, which is easy to Find the value of xy, x+y, and then solve