(2) 16-24(x-y)+9(x-y)^2=[4-3(x-y)]^2=(4-3x+3y)^2

(3)a^2-2a(b+c)+(b+c)^2=(a-b-c)^2

(4)4x^2-4x(y- 1)+(y-i)^2=(2x-y+ 1)^2

5( 1)-a+2a^2-a^3=-a( 1-2a+a^2)=-a(a- 1)^2

(2)3ax^2-3ay^2=3a(x^2-y^2)=3a(x+y)(x-y)

(3) 16a^2b- 16a^3-4ab^2=-4a(-4ab+4a^2+b^2)=-4a(2a-b)^2

6( 1)a^4- 1=(a^2+ 1)(a^- 1)=(a^2+ 1)(a+ 1)(a- 1)

(2)x^4- 18x^2+8 1=(x^2-9)^2=(x+3)^2(x-3)^2

(3)x^4y^4-8x^2y^2+ 16=(x^2y^2-4)^2=(xy+2)^2(xy-2)^2

2 means