二次根式的题型变化多样,往往需要根据题目的特点采用一些技巧.现介绍几个常用技巧,供解题时参考.1.发掘隐含条件例1已知y=x-2√+2-x√+8,求代数式x+yx√-y√-2xyxy√-yx√的值.解由已知得x-2≥0,2-x≥0 得x=2,从而y=8.原式=x+yx√-y√-2xyxy√(x√-y√)=x+yx√-y√-2xy√x√ The questions of the secondary roots vary in variety and often require the use of techniques based on the characteristics of the topic. Several commonly used techniques are now introduced for reference when solving a problem. 1. Examining implicit conditions Example 1 Known y=x-2√+2 -x√+8, find the value of the algebraic expression x+yx√-y√-2xyxy√-yx√. The solution is known to have x-2≥0,2-x≥0 and x=2, so y=8. Original =x+yx√-y√-2xyxy√(x√-y√)=x+yx√-y√-2xy√x√