MA2160:Quiz ??

(OverVector[v])=2 (OverVector[i])+a (OverVector[j])-2(OverVector[k])

With a=1 length of (OverVector[v]) is
A) 2
B) (Sqrt[5])
C) 3
D) 1
E) None of the above.

What value of a makes (OverVector[v]) parallel to (OverVector[w])=-6 (OverVector[i])+12(OverVector[j])-6(OverVector[k])
A) -2
B) 4
C) -4
D) 3
E) There is no such a.

The vector (OverVector[c]) is 
({{({{A)(OverVector[a])+(OverVector[b])                               ,  }, {B)(OverVector[a])-(OverVector[b])                               ,  }, {C)(OverVector[b])-(OverVector[a])                               ,  }, {D)-(OverVector[a])-(OverVector[b])                           ,  }, {E) None of the above.,          }}), }})

a = {1,2}
b={3,1}
Show[Graphics[{
Arrow[{{0,0},a}],
Text[" a ",a/2, Background->White],
Arrow[{{0,0},b}],
Text[" b ",b/2, Background->White],
Arrow[{a,b}],
Text[" c ",(a+b)/2,  Background->White]
}
]
]

?Arrow

?Arrow

?Arrow

A=Table[Sin[i]+Cos[j],{i,0.,9},{j,0.,9}];
Dimensions[A]
TableForm[Table[{j,Norm[A[[All,j]],2]},{j,1,10}]]