:(1). a^4-2a^2+1
=(a^2-1)^2
=(a-1)^2(a+1)^2
(2). (m+n)^2-6(m+n)+9
=(m+n-3)^2
(3). 9(a+b)^2-(a-b)^2
=(3a+3b+a-b)(3a+3b-a+b)
=(4a+2b)(2a+4b)
=4(2a+b)(a+2b)
(4). x^2(m-2)+(2-m)
=x^2(m-2)-(m-2)
=(m-2)(x^2-1)
=(m-2)(x-1)(x+1)
(1). a^4-2a^2+1 (2). (m+n)^2-6(m+n)+9 (3). 9(a+b)^2-(a-b)^2 (4). x^2(m-2)+(2-m)
=(m+n-3)^2 =(a-1)^2(a+1)^2 =4(2a+b)(a+2b) =(m-2)(x-1)(x+1)
(a^2-1)^2 (m+n-3)^2 4(2a+b)(a+2b) (m-2)(x+1)(x-1)