If →a=2^i+3^j+^k,→b=2^i+p^j+3^k and →c=2^i+17^j+3^k are coplanar vectors, then the value of p is
If →a and →b are vectors such that |→a+→b|=√29 and →a×(2^i+3^j+4^k)=(2^i+3^j+4^k)×→b, then a possible value of (→a+→b).(−7^i+2^j+3^k) is