A^2-b^2=(a-b)(a+b)
c^2-b^2=(c-b)(c+b)
1-b^2=(1-b)(1+b)
a^2-2^2=(a-2)(a+2)
16-b^2=4^2-b^2=(4-b)(4+b)
25a^2-b^2=(5a)^2-b^2=(5a-b)(5a+b)
m^2-36b^2=m^2-(6b)^2=(m-6b)(m+6b)
100-c^2=10^2-c^2=(10-c)(10+c)
9x^2-16y^2=(3x)^2-(4y)^2=(3x-4y)(3x+4y)
25c^2-4b^2=(5c)^2-(2b)^2=(5c-2b)(5c+2b)
49a^2-81b^2=(7a)^2-(9b)^2=(7a-9b)(7a+9b)
m^2-4y^2=m^2-(2y)^2=(m-2y)(m+2y)
x^2y^2-1=(xy)^2-1=(xy-1)(xy+1)
4-m^2n^2=2^2-(mn)^2=(2-mn)(2+mn)
(ac)^2-9=(ac)^2-3^2=(ac-3)(ac+3)
x^4-16=(x^2)^2-4^2=(x^2-4)(x^2+4)=(x-2)(x+2)(x^2+4)
36-m^6=6^2-(m^3)^2=(6-m^3)(6+m^3)
x^4-y^4=(x^2)^2-(y^2)^2=(x^2-y^2)(x^2+y^2)=(x-y)(x+y)(x^2+y^2)
c^4-4b^6=(c^2)^2-(2b^3)^2=(c^2-2b^3)(c^2+2b^3)