Question

根據下列兩組x、y的值，求出代數式的值．
（1）；                     
（2）滿足的x、y的值．

Answer 1

（1）當時，························································· （1分）
，···················································· （3分）
.··········································································· （4分）
（2）由非負性可知·························································· （6分）
當時，
，······················································ （7分）
.      （8分）

試題分析：（1）把x、y的值代入代數式，運用有理數的混合運算求值．
（2）利用絕對值和完全平方都大于或等于0得出x、y的值.
點評：熟練運用合并同類項的法則，利用絕對值和完全平方不小零從而列出方程求解．