已知空間中相異兩點A(-3,4,5),B(1,2,3),P點在xy平面上 ... - 隨意窩

1.向量X=(2,3,5),向量Y=(-4,a,-10b),若X//Y,求a=? b=?-2*(2,3,5)=(-4,-6,-10)= (-4,a,-10b)a=-6,b=12.於空間中,若三點A(-1,3,2),B(1,0,2),C(k+ 3m ,1,2k-m)共線,則k=? m=?AB=(2,-3,0)BC=(k+ 3m -1,1,2k-m-2)(2,-3,0)/(-3)=(-2/3,1,0)= (k+ 3m -1,1,2k-m-2)k+ 3m -1=-2/3k+ 3m =1/3  ---(1)2k-m-2=0, m=2k-2 , 代入(1)k=