第1章 1.11

(1)

$x^2 + 8x + 16 = (x + 4)^2$

(2)

$8x^2 + 24x + 18 = 2(4x^2 + 12x + 9) = 2(2x + 3)^2$

(3)

$x^2 - 14xy + 49y^2 = (x - 7y)^2$

(4)

$4p^3 - 20p^2q + 25pq^2 = p(4p^2 - 20pq + 25q^2) = p(2p - 5q)^2$

(5)

$a^2 + a + \frac{1}{4} = \left(a + \frac{1}{2}\right)^2$

(6)

$18a^2 - 8b^2 = 2(9a^2 - 4b^2) = 2(3a + 2b)(3a - 2b)$