当a-b=4,ab= -1时,求代数式(-2ab+2a+3b)-(3ab+2b-2a)-(ab+4a+b)的值

问题描述:

当a-b=4,ab= -1时,求代数式(-2ab+2a+3b)-(3ab+2b-2a)-(ab+4a+b)的值

(-2ab+2a+3b)-(3ab+2b-2a)-(a+4b+ab) =-2ab+2a+3b-3ab-2b+2a-a-4b-ab =-6ab+3a-3b =-6ab+3(a-b) 将a-b=4,ab=-1代入上式 原式=-6*(-1)+3*4=6+12=18 所以(-2ab+2a+3b)-(3ab+2b-2a)-(a+4b+ab)=18...