x² + x -1/(x² + x) = 3/2两边同时乘以(x² + x)得：(x² + x)² - 1 = 3(x² + x)/22(x² + x)² - 3(x² + x) - 2 = 0[2(x² + x) + 1 ][(x² + x) - 2] = 02(x
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