【简答题】设x,y∈R,向量 a =(x,1), b =(1,y), c =(2,-4)且 a ⊥ c , b ∥ c ,求 | a + b | .
【单选题】设 x , y ∈R,向量 a =( x, 1), b =(1, y ), c =(2,-4),且 a ⊥ c , b ∥ c ,则| a + b |= ( ).
【简答题】设A,B∈R,A≠B且AB≠0,则方程Bx-y+A=0和 x 2 B - y 2 A =1 在同一坐标系下的图象可能是( ) A. B. C. D.
【简答题】设x,y∈R,向量 a =(x,1), b =(1,y), c =(2,-4)且 a ⊥ c , b ∥ c ,则| a + b |=______.
【单选题】设x,y∈R,向量 a =(x,1), b =(1,y), c =(2,-4)且 a ⊥ c , b ∥ c ,则| a + b |=( )
【单选题】设y=Rx+b,当x=1时,y=1,当x=2时,y= -4,则R,b的值为 [ ]