Solve Coplanar Vector Problem with a, b, and c Vectors | Find all Values of t

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Homework Statement


Find all values of t so that the three vectors a=(1,2,3) b=(4,5,6) and c=(7,8,t) are coplanar.

Homework Equations


(axb) \bullet c=0

The Attempt at a Solution



(1, 2, 3) x (4, 5, 6)
(-3,6,-3)
(-3,6,-3)\bullet(7,8,t)
27=3t
t=9

it says find ALL values of t. i keep getting 9 through different combinations. is there only one value of t? thnks
 
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Yes, there is only one value of t. If you'd gotten 27=0*t for your last equation then any t would work. But you didn't.
 
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