1.) Show that

det ( 1+x 2 3 4

1 2+x 3 4

1 2 3+x 4

1 2 3 4+x)

= x^3 (x+10)

It should be easy but I dont know why I cannot get the answer :(

Please help!

2.) Consider the triangle ABC formed by the points A(3,2,1), B(4,4,2) and C(6,1,0). Find the coordinates of point D on BC such that AD is perpendicular to BC. (ans: 1/17 (80 50 22)T)

THANKS A LOT!!