2 、( 6+x)(6-x)
3 、( 2y- 1)?
4 、( a+b)(b-c)
5. One quarter of1(x-5y)(x+5y)
6 、( x+y-z)(x+y+z)
7 、( a-b)?
8、 1 1
9 、( xy- 1)?
10、3x? y-6x? y? +3xy? =3xy(x? -2xy+y? )=3xy(x-y)?
1 1, the fifth power of x, the fourth power of y+the fourth power of x, and the fifth power of y =x? y? (x+y)=(xy)? (x+y)=4
12、x(2-a)+x? (a-2)=(a-2)(x? -x)=(a-2)x(x- 1)
13,-9 1x? +49 4y? =(2y/7)? -(x/3)? =((2y/7)+(x/3))((2y/7)-(x/3))