若a-b等于4,ab等于1,求（-2ab+2a+3a)-(3ab+2b-2a)-(a+4b+ab)的值

题目

若a-b等于4,ab等于1,求（-2ab+2a+3a)-(3ab+2b-2a)-(a+4b+ab)的值

答案

把题目拆开啊
（-2ab+2a+3a)-(3ab+2b-2a)-(a+4b+ab)
=-2ab+2a+3a-3ab-2b+2a-a-4b-ab
=6a-6b-6ab
=6(a-b)-6ab (代入a-b=4 ab=1)
=6*4-6*1
=18