Hello,

you are only asked to calculate the direction of the plane not the equation of a specific plane. Therefore your method is OK. You should have got:

n = -12i + -10j + 14k

The plane runs through the point O and the vectors OP and OQ define the plane:

p = (0i + 0j + 0k) + r(i - j - 2k) + s(3i + 2j -k), r,s in IR

If you want to use the normal vector (-3, 7, 5) then the equation of the plane becomes:

-3x + 7y + 5z = 0