ab是两个不共线的向量,已知向量ab=3a+2b,向量cb=a+xb,向量cd=-2+b,若abc三点共线

AB = 3a+2b
CB = a+xb
CD = -2+b
A,B,C is on a straight line
To find x
AB = kCB
3a+2b = k(a+xb)
=>
3=k and 2=xk
=> x = 2/3那要是ABD共线呢CD=-2+b有问题，请对对题目CD=-2a+bAC = AB-CB= (3a+2b)-(a+xb)= 2a+(2-x)bCD= -2a+bACD 共线AC = kCD2a+(2-x)b = k(-2a+b)=>2= -2kand2-x=k=> 2-x = -1x= 3