( 1)3x^2- 12 = 3(x+2)(x-2)(2)x^3-4x=x(x+2)(x-2)

5. decompose the following factors: fill in the blanks.

( 1)4a^2 +4a+ 1=(2a+ 1)^2(2) 1+m+m^2/4=( 1+m/2)^2

6. If x+y=-4 and x-y=8, then the value of the algebraic expression X 2-Y 2 is -32.

7. Break down the following categories: writing process

( 1)ab^2-2a^2 b+a^3

=a(b^2-2ab+a^2)

=a(b-a)^2

(2)x^3 y-2x^2 y^2+xy^3

=xy(x^2-2xy+y^2)

=xy(x-y)^2

8. Simple calculation and writing process

( 1) 19.5^2-0.5^2

=( 19.5+0.5)( 19.5-0.5)

=20X 19

=380

(2) 56 2+44 2+56× 88 (this question is multiplied by ×)

=56^2+2x56x44+44^2

=(56+44)^2

= 100^2

= 10000