当题目中的未知数x、y具有对称关系时(即当x、y互换位置时,原式保持不变),如果令x+y=a,xy=b,用换元法进行解答,就可以使解题过程更简单.下面通过几道例题,帮助同学们掌握这种解题技巧在分式求值中的妙用.例1若x-1x=1,则x3-1x3的值为().A.3B.4C.5D.6解:设1x=y,则x-y=1,xy=1,所以 When the unknown numbers x, y in the title have a symmetric relationship (that is, when the x, y interchange positions, the original remains unchanged), if x + y = a, xy = b, with the replacement method to answer, The problem-solving process can be made easier. The following examples are used to help students master the magical skills of this problem solving technique in fractional evaluation. Example 1 If x-1x=1, the value of x3-1x3 is () .A.3B.4C.5D.6 Solution: Let 1x=y, then xy=1, xy=1, so