In R3 let S=span((1,2,4)^T)

What is a basis for S^(perpendicular)?

I know that 0=x*y=1y1+2y2+4y3

and that y2 and y3 are free variables so y1=-2y2-4y3

i have then tried to solve for each of the vectors this way but it is not correct.

Please help?

Thank You,

Diggidy