a) a⁴-b⁴ = (a²-b²)(a²+b²) = (a-b)(a+b)(a²+b²)
b) a⁴-1 = (a²-1)(a²+1) = (a-1)(a+1)(a²+1)
c) H(x) = x⁴-6x²+8 = x⁴-2x²-4x²+8 = x²(x²-2)-4(x²-2) = (x²-2)(x²-4) = (x²-2)(x-2)(x+2)
e) 16x⁴-81y⁴ = (4x²-9y²)(4x²+9y²) = (2x-3y)(2x+3y)(4x²+9y²)
f) 16a⁴-9 = (4a²-3)(4a²+3) = (2a-V3)(2a+V3)(4a²+3)
g) 81x⁴-25 = (9x²-5)(9x²+5) = (3x-V5)(3x+V5)(9x²+5)
d) 81-m⁴ = (9-m²)(9+m²) = (3-m)(3+m)(9+m²)
h) 81m⁸-16 = (9m⁴-4)(9m⁴+4) = (3m²-2)(3m²+2)(9m⁴+4)