x2y+
xy2=
xy(x+y)
B .
C .
D .
①x2﹣y2﹣1=(x+y)(x﹣y)﹣1;
②x3+x=x(x2+1);
③(x﹣y)2=x2﹣2xy+y2;
④x2﹣9y2=(x+3y)(x﹣3y).
B . a2+2a+2=(a+1)2+1
C . x2﹣1=(x+1)(x﹣1)
D . x2﹣y2=(x+y)(x﹣y)=x2﹣y2
)
B .
C .
D .
B .
C .
D .
)
C . x2﹣4+3x=(x+2)(x﹣2)+3x
D . x2﹣9=(x+3)(x﹣3)
B .
C .
D .
B .
C .
D .
B .
C .
D .