ive been struggling with these for an hour and a half. they arent hard, i just cant seem to make them work. the first one is: A = (5,3,2) B = (-1,4,6) C = (8,2,0) im using this format (x,y,z) aA+bB+ C = a vector parallel to the y-axis. so, that means i need to find a vector with only z components right? well, the answers out of the back of the book are a = -12/7 and b = -4/7. these dont work out. heres the second one A = (a,1,4) B = (3,b,-6) C = (5,-2,c) Im supposed to find a,b, and c so that all three vectors are perpendicular to each other. that means i should use the dot product with A and B, A and C, and B and C and set the dot product equal to zero for all three. So I did this, and i got answers for a, b and c but they dont work out when i check them.