F.2 maths (factorization) 2 questions

1) (a-2b)^2 + (2a-b) (2b-a)
=(a-2b)^2 - (2a-b) (a-2b) (係(2b-a)嗰度抽個負號出去就會變成(a-2b))
= (a-2b)( a-2b - (2a-b) )
=(a-2b)(a-2b-2a+b)
= (a-2b)(-a-b)

2) 2(p+q) ^2 - 6( p+q) ^3
= (2(p+q)^2 )( 1-3(p+q)) (有幾多相同既野就抽幾多出黎)
= (2(p+q)^2)(1-3p-3q)

3)2(x+y-1)^2 - 4(1-x-y)
= 2(x+y-1)^2 +4(x+y-1) (同第一條既做法一樣 都係抽個負號出黎，令兩邊都變成一樣，可以抽到出黎)
= (2(x+y-1))(x+y-1-2) (有幾多抽幾多)
= (2(x+y-1))(x+y-3)

4)5 m^2 n + m^2 ( 1-n) + 2m^ 2n
= 7m^2 n+ m^2 (1-n)
= m^2 (7n + (1-n))
= m^2( 7n+2-n)
= m^2 (6n+2)
希望幫到你啦!