第40页 - 江苏版实验班提优训练数学八年级上下册答案

$\sqrt{3²+2×3×\sqrt{5}+(\sqrt{5})^{2} }$

$\sqrt{(3+5)²}\ $

$|3+\sqrt{5}|$

$3+\sqrt{5}$

$ \begin{aligned} 解:原式&=\sqrt {(\frac{1}{2})²+2×\frac{1}{2}×\frac{\sqrt{3}}{2}+(\frac{\sqrt{3}}{2})^{2}} \\ &= \sqrt{(\frac{1}{2}+\frac{\sqrt{3}}{2})^{2} } \\ &=|\frac{1}{2}+\frac{\sqrt{3}}{2}| \\ &=\frac{1+\sqrt {3} }{2}. \\ \end{aligned}$

$8\sqrt 3+2\sqrt 3+3\sqrt 3+6\sqrt 3+\sqrt 3=20\sqrt 3$

$答：他们共走了20\sqrt{3}千米.$