要详细点..每一步都要列出来..
谢谢……
要详细点..每一步都要列出来..
谢谢……
(3a²—ab+7)—(—4a²+2ab+7)
=3a²—ab+7+4a²-2ab-7
=3a²+4a²—ab-2ab+7-7
=(3+4)a²—(1+2)ab+(7-7)
=7a²—3ab+0
=7a²—3ab
(3a²—ab+7)—(—4a²+2ab+7)
=3a²—ab+7+4a²—2ab—7
=(3a²+4a²)+(—2ab—ab)+(7—7)
=(3+4)a²+(—2—1)ab+(7—7)
7a²—3ab
(3a²—ab+7)—(—4a²+2ab+7)
=3a²-ab+7+4a²-2ab-7
=7a²-3ab
a(7a-3b)
(3a²—ab+7)—(—4a²+2ab+7)
=3a²+4a²-ab-2ab+7-7
=7a²-3ab
(3a²—ab+7)—(—4a²+2ab+7)
=3a²—ab+7+4a²-2ab-7
=3a²+4a²-ab-2ab+7-7
=7a²-3ab