(x2-6)2-25x2
=(x²－6)－(5x)²
=(x²－6＋5x)(x²－6－5x)
=(x＋6)(x－1)(x－6)(x＋1)
1-(m2-2m)2
=(1＋m²－2m)(1－m²＋2m)
=(m－1)²(1－m²＋2m)
-81y5+y
=﹣y(81y⁴－1)
=﹣y（9y²＋1）（9y²－1）
=﹣y（9y²＋1）(3y＋1)(3y－1)