1.=(a+b)^2-1 =(a+b+1)(a+b-1)2.=(4m-n)^2-49 =(4m-n+7)(4m-n-7)3.=(x-2)^2-y^2 =(x-2+y)(x-2-y)4.=(5a+1)^2-9b^2 =(5a+1+3b)(5a+1-3b)
