Call the given points A, B, and C. Then the cross product AB×AC will be normal to the plane, so will tell what the coefficients in the plane's equation might be.
AB = (-2, 1, 1)
AC = (2, 6, -4)
AB×AC = (-10, -6, -14)
Dividing a factor of -2 from these coefficients, and using point B to determine the constant, we have the equation for the plane ...
