14.
(9a-b²)(b²+9a) = (9a)² - (b²)² = 81a²-b^4
(4+y²)(4-y²) = (4)² - (y²)² = 16 - y^4
(7+3y)(7-3y) = (7)² - (3y)² = 49 - 9y²
(8c+9d)(9d-8c)= (9d)² - (8c)² = 81d² - 64c²
15.
8 - 1/8*a³ = 2³ - (1/2*a)³ = (2-1/2*a)(4 + a + 1/4 * a²)
1+27y³ = 1³ + (3y)³ = (1+3y)(1 - 3y + 9y²)
x³-64 = x³ - 4³ = (x-4)(x² + 4x + 16)
1/64*m³+1000 = (1/4*m)³ + 10³ = (1/4*m+10)(1/8*m² - 2.5m + 100)
16.
(b+3)² = b² + 6b + 9
(y+9)² = y² + 18y + 81
(m-0.3)² = m² - 0.6m + 0.09
(a-25)² = a² - 50a + 625