1.1/2x²-8ax+32a²
=1/2(x²-16ax+64a²)
=1/2(x-8a)²
2.x²(x²-y²)+z²(y²-x²)
=x²(x²-y²)-z²(x²-y²)
=(x²-y²)(x²-z²)
=(x+y)(x-y)(x+z)(x-z)
3.5a²b(x-y)³-30ab²(y-x)²
=5a²b(x-y)³-30ab²(x-y)²
=5ab(x-y)²[a(x-y)-6b]
=5ab(x-y)²(ax-ay-2b)