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

（1）当时，························································· （1分）
，···················································· （3分）
.··········································································· （4分）
（2）由非负性可知·························································· （6分）
当时，
，······················································ （7分）
.      （8分）

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.
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．