If a, b and c are non-coplanar vectors and if d is such that `d = (1)/(x) (a + b + c) and a = (1)/(y) (b + c + d)` where x and y are non-zero real numbers, then `(1)/(xy) (a + b + c + d) =`

If bar(a), bar(b)&bar(c) are non-coplanar vectors and if bar(d) is such that bar(d)=1/x(bar(a)+bar(b)+bar(c)) and bar(d)=1/y(bar(b)+bar(c)+bar(d)) where x and y are non-zero real numbers, then 1/(xy)(bar(a)+bar(b)+bar(c)+bar(d))=

If a, b and c are non-coplanar vectors and d=lambda vec a+mu vec b+nu vec c , then lambda is equal to

If (ax + b/y) prop (cx + d/y) and a, b, c, d are non zero constants, then

If (a^(2)+b^(2)+c^(2))(b^(2)+c^(2)+d^(2))<=(ab+bc+cd)^(2) where a,b,c,d are non-zero real numbers,then they are in