Question

设a,b为不共线的非零向量,向量AB=2a+3b,BC=-8a-2b,CD=-6a-4b

Answer 1

|AD|=|AB + BC + CD| = |-12a - 3b | = 3 * |4a + b|

|BC| = 2 * |4a + b|

若4a+b=0,则a,b共线,舍弃.

因此,4a+b ≠ 0,|AD| > |BC|