Question

根据下列两组x、y的值，求出代数式的值．

（1）；                     

（2）满足的x、y的值．

 

Answer 1

【答案】

（1）当时，···················································································· （1分）

，·································································· （3分）

.······························································································· （4分）

（2）由非负性可知········································································ （6分）

当时，

，···································································· （7分）

.          （8分）

【解析】

试题分析：（1）把x、y的值代入代数式，运用有理数的混合运算求值．

（2）利用绝对值和完全平方都大于或等于0得出x、y的值.

考点：代数式求值；绝对值；完全平方．

点评：熟练运用合并同类项的法则，利用绝对值和完全平方不小零从而列出方程求解．