I need help solving these problems.

6) Determine the domain of the vector valued functions r(t) = r(t) = 7) Find an equation of the plane that passes through the points P (1, 3, 2), Q (3, -1, 6), and R (5, 2, 0). 8) Find the point at which the line with parametric equations 96 = 2 + 31? , y = '41 ,Z = 5+t intersects the plane4x + 53"22 =18 . 9) Find the angle between the planes x + y + Z =1 and x 2y + 32 =1 .Find symmetric equations for the line of intersection of these two planes