① 25x^4-10x^2+1=(5x²)²-2×5x²×1+1²=(5x²-1)² ②16（a-b)^2-9(a+b)^2=[4(a-b)]²-[3(a+b)]²=(4a-4b+3a+3b)(4a-4b-3a-3b)=(7a-b)(a-7b) ③m(a-b)-5（b-a)=m(a-b)+5(a-b)=(...