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-{-[-(-a )2-b2 ]}-[-(-b2)];
-b2+14ab+A=7a2+4ab-2b2,则A=________.
(a2-b2)-(a-b)(a+b)等于
A.-2b2
B.0
C.2a2
D.2a2-2b2
b2-(a-b+c)2因式分解为
A.(b+a+b+c)(b-a+b-c)
B.(b+a-b+c)(2b+a+c)
C.(a+c)(2b-a+c)
D.(a+c)(2b-a-c)