已知向量a=(2,-1),b=(x,-2) c=(3,y) 若a‖b,(a+b)⊥(b-c),求x+y

已知向量a=(2,-1),b=(x,-2) c=(3,y) 若a‖b,(a+b)⊥(b-c),求x+y
已知向量a=(2,-1),b=(x,-2) c=(3,y) 若a‖b,(a+b)⊥(b-c),求x+y

已知向量a=(2,-1),b=(x,-2) c=(3,y) 若a‖b,(a+b)⊥(b-c),求x+y
x+y= 0,
a‖b,
2*(-2)-(-1)*X=0,
X=4,
(2+X)(X-3)+(-3)*(-2-Y)=0,
Y=-4.
X+Y=4-4=0.