find the modulus direction cosin unit vector 1)4a-2b+3c, 2)a-7b+5c, 3)4a-3b+c.

Answer 1

assuming the usual i,j,k for directions,
|4i-2j+3k| = √(16+4+9) = √29
direction cosines are (4/√29,-2/√29,3/√29)