第2章 2.5

(1)

$\sqrt{25} = \sqrt{5^2} = 5$

(2)

$\sqrt{(-7)^2} = \sqrt{7^2} = 7$

(3)

$\sqrt{(-2)^2 5^2} = \sqrt{2^2 5^2} = 2 \cdot 5 = 10$

(4)

$\frac{\sqrt{(-4)^2}}{\sqrt{2^2}} = \frac{\sqrt{4^2}}{2} = \frac{4}{2} = 2$