point charges, Q1 (4,0,-3) and Q2 (2,0,1). Q2 = 4 nC, find Q1 such that the a. electric field at (5,0,6) has no z component. b. force on a test charge at (5,0,6) has no x component. heres what i did for a: i found the distance from Q1 to (5,0,6) to be the square root of 82 distance from Q2 to (5,0,6) to be square root of 34. i than found the unit vectors. multipled by the charges and set the z components equal. so i had 9Q1/sqr rt 82 = - 4nc*5/sqr rt 34 ended up with Q1 = -3.41 nc. answer in the back of the book says -3.463 on the second part i found the two forces using (Q*Qt)/4*pi*Eo*R^2. i than multiplied these by the unit vectors in the x direction and set one of them equal to negative the other and solved for Q1. i ended up with an answer of -48nC, the book says -18nC.