2x⁴ - 8x²
common factor is 2x²
therefore, you need to divide everything by 2x²
2x⁴ ÷ 2x² = x²
8x² ÷ 2x² = 4
2x² (x²-4)
for x²-4, you can also factor that using difference of squares
which is a² - b² = (a+b)(a-b)
x²-4 = (x+2)(x-2)
final answer: 2x² (x+2)(x-2)