1 a²b²-m²=(ab+m)(ab-m)
2 (m-a)²-(n+b)²=(m-a+n+b)(m-a-n-b)
3 x²-(a+b-c)²=(x+a+b-c)(x-a-b+c)
4 16x^4+81y^4
=16x^4+81y^4+72x²y²-72x²y²
=(4x²+9y²)²-72x²y²
=(4x²+6√2xy+9y²)(4x²-6√2xy+9y²)
5 (x+y)²-(x-y-1)²
=(x+y+x-y-1)(x+y-x+y+1)
=(2x-1)(2y+1)
6 a³-ab²=a(a²-b²)=a(a+b)(a-b)
7 x^3y^2-x^5=x³(y²-x²)=x³(y+x)(y-x)