已知a+b=2,ab=-1/2,求(a-6b=2ab)-(3a-4b=5ab)的值

已知a+b=2,ab=-1/2,求(a-6b=2ab)-(3a-4b=5ab)的值
已知a+b=2,ab=-1/2,求(a-6b=2ab)-(3a-4b=5ab)的值

已知a+b=2,ab=-1/2,求(a-6b=2ab)-(3a-4b=5ab)的值
(a-6b+2ab)-(3a-4b+5ab)
=a-6b+2ab-3a+4b-5ab
=-2a-2b-3ab
=-2(a+b)-3ab
=-2*2-3*(-1/2)
=-4+3/2
=-5/2