已知a-b=5,ab=-1,求(3b+a-2ab)-2(b-3.5a-ab)+3(ab+2a-5b)的值_数学解答

已知a-b=5,ab=-1,求(3b+a-2ab)-2(b-3.5a-ab)+3(ab+2a-5b)的值

人气：128 ℃　时间：2020-04-22 20:11:06

解答

(3b+a-2ab)-2(b-3.5a-ab)+3(ab+2a-5b)
=3b+a-2ab-2b+7a+2ab+3ab+6a-15b
=-14b+14a+3ab
=14(a-b)+3ab
=14×5-3
=70-3
=67