1. 已知$\left\{\begin{array}{l} x= 4,\\ y= -2\end{array} \right. 与\left\{\begin{array}{l} x= -2,\\ y= 8\end{array} \right. 都是方程y= ax+b$的解,求$a+b$的平方根.

解：把$\left\{\begin{array}{l} x = 4,\\ y = -2\end{array}\right.$与$\left\{\begin{array}{l} x = -2,\\ y = 8\end{array}\right.$代入方程$y = ax + b$得
$\left\{\begin{array}{l} 4a + b = -2,\\ -2a + b = 8.\end{array}\right.$解得$\left\{\begin{array}{l} a = -\frac{5}{3},\\ b = \frac{14}{3}.\end{array}\right.$
$a + b = -\frac{5}{3} + \frac{14}{3} = 3$，3的平方根是$\pm\sqrt{3}$，即$a + b$的平方根是$\pm\sqrt{3}$。

2. 我国古代数学名著《孙子算经》上有这样一道题:今有鸡兔同笼,上有三十五头,下有九十四足,问鸡兔各几何.
设鸡有x只,兔有y只,请你写出关于x,y的二元一次方程组,并解这个方程组.

解：由题意得$\left\{\begin{array}{l} x + y = 35,\\ 2x + 4y = 94.\end{array}\right.$
解得$\left\{\begin{array}{l} x = 23,\\ y = 12.\end{array}\right.$

五、趣味题
如图所示,小强和小红一起搭积木.小强所搭的“小塔”高度为23 cm,小红所搭的“小树”高度为22 cm.设每块A型积木的高为x cm,每块B型积木的高为y cm,求出x和y的值.
x=，y=。

$x = 4$，$y = 5$。